Immunoserology of Lyme

IgG Borrelia afzelii The IgG Borrelia afzelii test measures antibodies against Borrelia afzelii, one of the main bacterial species that cause Lyme disease in Europe and Asia. Unlike Borrelia burgdorferi (more common in North America), B. afzelii is especially associated with chronic skin forms of Lyme disease, such as acrodermatitis chronica atrophicans (ACA). What IgG B. afzelii Means IgG antibodies generally appear weeks to months after infection and often persist long-term, even after treatment. A positive IgG B. afzelii result suggests past exposure or ongoing immune memory to the bacteria, which may help clinicians determine whether symptoms are linked to later or chronic stages of Lyme disease. In contrast, IgM antibodies are more indicative of recent infection, so IgG testing provides a complementary view of the immune timeline. Clinical Importance Testing for IgG B. afzelii can be helpful in patients with: Persistent or late-stage Lyme symptoms, particularly skin changes such as ACA Neurological or musculoskeletal issues suspected to be related to European Lyme disease strains A history of tick exposure in endemic regions of Europe or Asia Patient Takeaway A positive IgG B. afzelii result indicates that your immune system has previously recognized this strain of Borrelia. This does not always mean there is an active infection, since IgG can remain detectable for years. Your healthcare provider will interpret the result in the context of your symptoms, exposure history, and other Lyme disease tests.

IgG Borrelia burgdorferi sensu stricto The IgG Borrelia burgdorferi sensu stricto (s.s.) test measures antibodies against the primary species of Borrelia that causes Lyme disease in North America and parts of Europe. This species is strongly linked to arthritis, neurological symptoms, and late-stage Lyme manifestations. What IgG B. burgdorferi s.s. Means IgG antibodies usually appear weeks to months after infection and can remain detectable long after the initial illness. A positive IgG result indicates past exposure or immune memory to B. burgdorferi s.s. and may support the diagnosis of later or persistent Lyme disease. Because IgM antibodies reflect recent infection, IgG testing is often used to assess whether symptoms may be related to a longer-term or chronic stage of infection. Clinical Importance Testing for IgG B. burgdorferi s.s. is most useful in patients who have: Arthritis or joint swelling that develops weeks to months after a tick bite Neurological problems such as meningitis, facial palsy, or peripheral neuropathy Chronic or recurrent Lyme symptoms with a history of tick exposure in endemic areas Patient Takeaway A positive IgG B. burgdorferi s.s. result means your immune system has previously recognized this Lyme-causing bacterium. This does not necessarily confirm an active infection, since IgG antibodies often stay in the blood for years. Your healthcare provider will always interpret the result together with your symptoms, clinical history, and other Lyme disease tests. If your IgG result is reported as equivocal (borderline), antibody levels are near the cutoff and not clearly positive or negative. In this case, repeat or confirmatory testing is usually recommended.

The IgG Borrelia burgdorferi Antigen (Ag) test measures long-term antibodies against antigens of Borrelia burgdorferi, the main bacterium responsible for Lyme disease, particularly in North America. Unlike species-specific tests that focus on one strain, antigen-based assays detect immune responses to a broader range of Borrelia proteins, offering insight into both past exposure and potential later-stage infection. What IgG B. burgdorferi Ag Means IgG antibodies appear weeks to months after infection and may remain present for years, even after treatment. A positive result suggests that your immune system has mounted a previous response to Borrelia antigens, which can be a clue in cases of chronic or late-stage Lyme disease. Because antigens cover multiple Borrelia proteins, this test may capture antibody responses that complement other markers such as OspC, OspA, or VlsE. Clinical Importance Testing for IgG Borrelia burgdorferi Ag can be helpful in patients who have: Persistent Lyme symptoms such as joint pain, neurological issues, or fatigue Evidence of late-stage disease, including Lyme arthritis or neuroborreliosis A history of tick exposure in Lyme-endemic areas where infection risk is high Patient Takeaway A positive IgG B. burgdorferi Ag test means your immune system has recognized antigens from the Lyme disease bacterium. This does not always indicate an active infection, since IgG antibodies may persist long after the original illness. Your healthcare provider will interpret the result together with your symptoms, clinical history, and other Lyme disease markers to build a complete diagnostic picture. If your result is equivocal (borderline), antibody levels are near the cutoff and the finding is uncertain. In these cases, repeat or confirmatory testing is often recommended.

The IgG Borrelia garinii test detects antibodies against Borrelia garinii, one of the main bacterial species in the Borrelia burgdorferi sensu lato complex that causes Lyme disease, particularly in Europe and Asia. This strain is strongly linked with neurological forms of Lyme disease (neuroborreliosis), including meningitis, radiculitis, and cranial nerve involvement. What IgG B. garinii Means IgG antibodies typically appear weeks to months after infection and can remain detectable long after the initial exposure. A positive IgG B. garinii result suggests past exposure or immune memory and may support the diagnosis of later or persistent Lyme disease, especially when neurological symptoms are present. Since IgM antibodies reflect recent infection, IgG testing helps assess whether symptoms may relate to chronic or long-term stages of Lyme disease. Clinical Importance Testing for IgG Borrelia garinii is most useful in patients with: Neurological symptoms such as meningitis-like signs, facial palsy, or nerve pain Chronic or persistent Lyme symptoms following tick exposure in endemic regions Musculoskeletal or systemic issues suspected to be caused by European or Asian Lyme strains Patient Takeaway A positive IgG B. garinii result means your immune system has previously recognized this Lyme-associated bacterium. This does not always indicate an active infection, since IgG antibodies can persist for years after exposure. Your doctor will interpret the result in the context of your symptoms, medical history, and other Lyme disease test findings. If your result is equivocal (borderline), antibody levels are near the cutoff and not clearly positive or negative. In such cases, repeat or confirmatory testing is often recommended.

The IgG Borrelia miyamotoi test detects antibodies against Borrelia miyamotoi, a tick-borne bacterium closely related to Lyme disease pathogens but classified as a relapsing fever Borrelia species. Unlike Borrelia burgdorferi sensu lato (which causes classical Lyme disease), B. miyamotoi is associated with hard-tick relapsing fever (HTRF) and can cause recurring fever episodes, flu-like symptoms, and in some cases, neurological complications. What IgG B. miyamotoi Means IgG antibodies usually develop weeks after infection and may remain detectable for months or years, even after symptoms resolve. A positive IgG result suggests past exposure or immune memory to B. miyamotoi. Because IgM reflects more recent infection, IgG testing provides insight into later or ongoing immune responses. Clinical Importance Testing for IgG Borrelia miyamotoi is particularly useful in patients with: Relapsing fever symptoms such as recurrent fever, chills, sweats, or fatigue Neurological complaints, including headache, meningitis-like symptoms, or confusion A history of tick exposure in areas where Lyme disease and relapsing fever Borrelia overlap (Europe, Asia, North America) Patient Takeaway A positive IgG B. miyamotoi result means your immune system has previously recognized this relapsing fever Borrelia. This does not always indicate an active infection, since IgG antibodies can persist after past exposure. Your healthcare provider will interpret the result in combination with your symptoms, exposure history, and other Borrelia test results to determine next steps. If your result is reported as equivocal (borderline), antibody levels are near the cutoff and the finding is uncertain. In this case, repeat or confirmatory testing may be recommended.

The IgG Babesia test measures antibodies against Babesia species, a group of parasites transmitted by ticks that can cause babesiosis, a malaria-like illness. Babesia microti is the most common species in North America, while Babesia divergens and others are more frequently found in Europe and Asia. What IgG Babesia Means IgG antibodies typically develop several weeks after infection and may remain detectable for months or years, even after treatment. A positive IgG result usually indicates past exposure or immune memory, not necessarily an active infection. IgM antibodies are more reflective of recent or acute babesiosis, while IgG testing provides a view of longer-term immune response. Clinical Importance Testing for IgG Babesia can be helpful in patients who have: Unexplained fevers, sweats, or chills that resemble malaria-like illness Fatigue, anemia, or low platelets, which can result from parasite activity in red blood cells A history of tick exposure, particularly in areas where Lyme disease and babesiosis often occur together (co-infections are common) Persistent or recurrent symptoms after suspected tick-borne infection Patient Takeaway A positive IgG Babesia result means your immune system has previously recognized the parasite, suggesting prior exposure or infection. Since IgG can remain long after illness, this test does not always mean the infection is still active. Your healthcare provider will interpret the result alongside your symptoms, clinical history, and other tests (such as IgM, PCR, or blood smear) to confirm whether babesiosis is present. If the result is equivocal (borderline), antibody levels are close to the cutoff and not clearly positive or negative. In this case, repeat or confirmatory testing is often recommended.

The IgG Bartonella test measures antibodies against Bartonella species, a group of bacteria transmitted by ticks, fleas, or scratches from infected animals (especially cats). Bartonella henselae and Bartonella quintana are the most common human pathogens. Infection can lead to cat scratch disease, trench fever, or tick-borne bartonellosis, which may cause persistent systemic or neurological symptoms. What IgG Bartonella Means IgG antibodies generally appear weeks after infection and can remain detectable for months or years. A positive IgG result usually indicates past exposure or immune memory rather than an active infection. Because IgM antibodies reflect recent or acute infection, IgG testing is more useful for identifying later or chronic immune responses. Clinical Importance Testing for IgG Bartonella can be useful in patients with: Persistent fatigue, fever, or swollen lymph nodes Neurological complaints such as headaches, neuropathy, or cognitive issues Joint or muscle pain that overlaps with other tick-borne illnesses A history of tick bites, cat exposure, or flea bites in areas where Bartonella is present Suspected co-infections, since Bartonella is often found alongside Lyme disease and Babesia Patient Takeaway A positive IgG Bartonella result means your immune system has previously recognized Bartonella, suggesting prior exposure or infection. However, IgG alone does not confirm whether the infection is still active, as antibodies may persist long after initial illness. Your healthcare provider will interpret the result alongside your symptoms, medical history, and other diagnostic tests (such as IgM, PCR, or culture-based methods). If the result is equivocal (borderline), antibody levels are close to the cutoff and not clearly positive or negative. In these cases, repeat or confirmatory testing is usually recommended.

The IgG Ehrlichia test measures antibodies against Ehrlichia species, bacteria transmitted by ticks that cause ehrlichiosis, a potentially serious tick-borne illness. The two main human pathogens are Ehrlichia chaffeensis (human monocytic ehrlichiosis, HME) and Ehrlichia ewingii. Infections can lead to fever, chills, muscle aches, headache, and sometimes severe complications if untreated. What IgG Ehrlichia Means IgG antibodies typically develop within 2–4 weeks after infection and may remain present for months or years. A positive IgG result usually indicates past exposure or immune memory to Ehrlichia. Since IgM antibodies reflect more recent infection, IgG testing is most useful for assessing later or past stages of ehrlichiosis. Clinical Importance Testing for IgG Ehrlichia can be important in patients with: Unexplained fever, fatigue, headache, or muscle pain following a tick bite Low white blood cell counts, low platelets, or abnormal liver tests often seen in ehrlichiosis Persistent or relapsing symptoms after tick exposure in endemic regions Suspected co-infections with other tick-borne pathogens such as Borrelia (Lyme disease) or Babesia Patient Takeaway A positive IgG Ehrlichia result means your immune system has recognized the bacteria at some point, suggesting prior exposure or infection. This does not always mean the infection is currently active, since IgG antibodies may persist long-term. Your healthcare provider will interpret this result together with your symptoms, tick exposure history, and other test results (including IgM, PCR, or blood smear) to determine whether ehrlichiosis is active or past. If your result is reported as equivocal (borderline), antibody levels are close to the cutoff and not clearly positive or negative. In these cases, repeat or confirmatory testing is often recommended.

The IgG Immunodominant Peptide C6 (P. C6) test detects antibodies against a highly conserved region of the VlsE protein from Borrelia burgdorferi, the main bacterium that causes Lyme disease. The C6 peptide is considered an immunodominant epitope—a portion of the protein that triggers a strong and reliable immune response across different strains of Borrelia. What IgG P. C6 Means IgG antibodies to C6 usually appear several weeks after infection and remain detectable during later stages of Lyme disease. A positive result suggests past or ongoing immune recognition of Borrelia, making this test useful for identifying later-stage or persistent infection. Because C6 is highly conserved, the test can detect antibody responses across different Borrelia species, improving diagnostic sensitivity. Clinical Importance Testing for IgG P. C6 can be particularly valuable in: Patients with suspected Lyme disease who are beyond the early infection window Individuals with joint, neurological, or chronic symptoms linked to Lyme Confirmatory testing, as C6 is often used alongside other Borrelia markers (OspC, OspA, VlsE) to increase accuracy Patient Takeaway A positive IgG P. C6 result means your immune system has recognized the C6 peptide of Borrelia, suggesting exposure to the Lyme disease bacterium. This does not always prove an active infection, since IgG can persist after prior illness, but it is considered a reliable marker of Borrelia exposure. Your healthcare provider will compare this result with your symptoms, tick exposure history, and other Lyme disease tests for a complete interpretation. If your result is equivocal (borderline), antibody levels are close to the cutoff and the finding is uncertain. In this case, repeat or additional confirmatory testing may be recommended.

The IgG LFA Antigen + CK10 test evaluates long-term antibody responses to both Borrelia antigens (using a lateral flow assay, or LFA) and Cytokeratin 10 (CK10), a structural protein found in epithelial tissues such as the skin. This combined test helps clinicians explore the connection between infection-driven immune responses and autoimmune reactivity. What IgG LFA Antigen + CK10 Means IgG antibodies usually appear weeks after infection and remain detectable long-term as part of immune memory. A positive IgG LFA antigen result suggests past exposure to Borrelia or related tick-borne pathogens. The detection of IgG antibodies against CK10 may point toward autoimmune activity involving epithelial tissues, which can sometimes develop after infection-triggered immune responses. Clinical Importance This test may be most useful in patients who have: Chronic or unexplained skin symptoms such as rashes, blistering, or inflammatory dermatoses Persistent immune symptoms following a suspected tick-borne infection Overlap of infection and autoimmunity, where Borrelia exposure may have triggered autoimmune processes Complex or long-standing multi-system symptoms that are difficult to classify with single-marker tests Patient Takeaway A positive IgG LFA Antigen + CK10 result indicates that your immune system has previously recognized Borrelia antigens and may also be reacting to CK10, a self-protein in epithelial tissues. This combination can provide important clues about both past infection and possible autoimmune involvement. Your healthcare provider will interpret the result in the context of your symptoms, medical history, and additional laboratory findings. If your test is reported as equivocal (borderline), antibody levels are close to the cutoff and not clearly positive or negative. In this case, repeat or confirmatory testing is usually recommended.

What is it? The IgG Outer Surface Proteins A and C (OspA & OspC) test is a blood test that measures your immune system’s production of IgG antibodies against specific proteins on the surface of Borrelia burgdorferi, the bacteria that causes Lyme disease. Outer Surface Proteins (Osp) are molecules the bacteria use to survive and infect humans: OspA helps the bacteria persist in ticks. OspC plays a key role in establishing infection in people. When your immune system encounters Borrelia burgdorferi, it may produce IgG antibodies targeting these proteins. Detecting these antibodies can help provide clues about whether your body has mounted a response to Lyme disease. Why is this marker important? A positive IgG OspA/OspC result suggests that your body has been exposed to the Lyme bacteria in the past and created antibodies. IgG antibodies usually appear weeks to months after infection, so they are more commonly seen in later or persistent stages of Lyme disease. This test is often used alongside other Lyme disease tests (such as IgM antibodies, ELISA, or Western blot) to give a more complete diagnostic picture. How to interpret results Elevated IgG OspA/OspC Suggests past exposure or possible ongoing infection with Borrelia burgdorferi Typically appears in later or chronic phases of the disease Levels may stay elevated for years, even after successful treatment Normal or Negative IgG OspA/OspC May mean no prior exposure Could also mean antibodies have not yet developed (common in very early Lyme disease, known as the “window period”) Repeat testing may be considered if symptoms suggest Lyme but the initial test is negative Symptoms often linked with Lyme disease People who test positive for Lyme markers often recall symptoms such as: Early stage: bull’s-eye rash (erythema migrans), fever, chills, muscle aches, fatigue Later stage: joint pain, headaches, nerve pain, memory or concentration problems, irregular heartbeat What can affect this test? Stage of infection: IgG develops later, so it’s not reliable for early detection Immune system health: Those with weakened immunity may not produce strong antibodies Previous infection: IgG antibodies may persist long after treatment and recovery What to do if your results are elevated An elevated result by itself does not confirm active Lyme disease. Your healthcare provider will interpret these findings together with: Your symptoms and medical history Other Lyme tests (IgM, ELISA, Western blot, or PCR) Possible tick exposure in Lyme-endemic areas If Lyme disease is suspected, your doctor may recommend antibiotic treatment tailored to the stage and presentation of the illness. Key takeaway The IgG OspA/OspC test shows whether your immune system has produced longer-term antibodies to Lyme disease bacteria. A positive result indicates past or possible ongoing exposure, but it does not by itself prove an active infection. Your doctor will combine this result with your symptoms, exposure history, and additional tests to make the most accurate diagnosis and treatment plan.

The IgG OspE test measures antibodies against Outer Surface Protein E (OspE) of Borrelia burgdorferi, one of the proteins that help the bacterium evade the immune system and persist in the body. OspE belongs to the Erp (OspE-related proteins) family, which plays a key role in protecting Borrelia from complement-mediated killing by binding to host factor H. What IgG OspE Means IgG antibodies against OspE typically develop weeks to months after infection and may remain detectable long after exposure. A positive IgG OspE result indicates past immune recognition of Borrelia, which can support the diagnosis of later or persistent Lyme disease. Because OspE helps Borrelia survive in the bloodstream, IgG detection may be especially relevant in patients with disseminated or chronic forms of infection. Clinical Importance Testing for IgG OspE may be most useful in patients with: Persistent or late-stage Lyme symptoms such as arthritis, fatigue, or neurological complaints Evidence of Borrelia dissemination, where immune evasion mechanisms are important Chronic or relapsing illness following a history of tick exposure in endemic regions Suspected co-infections, where broader immune profiling improves diagnostic accuracy Patient Takeaway A positive IgG OspE result suggests your immune system has previously recognized this Borrelia surface protein, pointing to past or ongoing exposure. However, IgG antibodies can remain in the body long after the initial infection, so the result does not confirm whether the infection is still active. Your healthcare provider will interpret the result alongside your symptoms, clinical history, and additional Lyme disease markers (such as OspC, OspA, or VlsE/C6). If your IgG OspE result is equivocal (borderline), antibody levels are near the cutoff and not clearly positive or negative. In such cases, repeat or confirmatory testing may be recommended.

The IgG VmpE test measures antibodies against Variable Major Protein E (VmpE), a surface protein produced by Borrelia burgdorferi, the bacterium that causes Lyme disease. VmpE belongs to a family of variable major proteins (Vmps) that the bacteria can change through a process called antigenic variation. This ability allows Borrelia to evade immune detection and sometimes persist in the body. What IgG VmpE Means IgG antibodies generally appear weeks after infection and remain detectable long-term as part of immune memory. A positive IgG VmpE result suggests past or ongoing immune recognition of Borrelia. Because VmpE changes its structure to avoid the immune system, IgG reactivity may reflect exposure during persistent or relapsing stages of infection. This test complements other Borrelia markers (such as OspC and VlsE) by giving additional insight into how the immune system responds to Borrelia’s evasion strategies. Clinical Importance Testing for IgG VmpE may be useful in patients with: Chronic or relapsing Lyme symptoms, such as fatigue, joint pain, or neurological issues Suspected persistent infection, where Borrelia may continue to vary its surface proteins Unexplained immune activity after a history of tick exposure in endemic areas Patient Takeaway A positive IgG VmpE result means your immune system has previously recognized this variable Borrelia protein. This points to prior or ongoing exposure, but IgG antibodies alone cannot confirm an active infection, since they may persist long after the illness. Your healthcare provider will interpret the result together with your symptoms, medical history, and other Lyme disease markers. If the IgG VmpE result is equivocal (borderline), antibody levels are close to the cutoff and not clearly positive or negative. In this case, repeat or confirmatory testing is usually recommended.

IgM B. afzelii – Research Overview IgM B. afzelii testing measures the presence of early antibodies directed against Borrelia afzelii, one of the major European subspecies of the Lyme disease–causing bacteria within the Borrelia burgdorferi sensu lato complex. While B. burgdorferi sensu stricto is most common in North America, B. afzelii is a leading cause of Lyme borreliosis in Europe and Asia. The Role of IgM Antibodies The immune system produces IgM antibodies soon after exposure to Borrelia species. In the case of B. afzelii, IgM antibodies typically appear within the first 1–3 weeks following a tick bite. Detecting IgM can indicate: Recent or early infection with B. afzelii. An ongoing immune response in symptomatic individuals. Possible non-specific reactivity or cross-reactivity, which is why results near the cut-off require careful interpretation. Clinical Significance of B. afzelii Unlike other Borrelia subspecies, B. afzelii is strongly associated with dermatological forms of Lyme disease, including: Acrodermatitis chronica atrophicans (ACA): a late-stage, chronic skin condition. Erythema migrans: the classic early “bull’s-eye” rash. Other chronic or recurrent skin manifestations. Because of these clinical patterns, detection of IgM antibodies against B. afzelii is particularly useful in European patients presenting with skin changes, joint involvement, or unexplained neurological symptoms. Limitations and Considerations False positives may occur due to cross-reactivity with other infections or immune system activity. An isolated IgM response without IgG development should be interpreted with caution, especially beyond the first 6–8 weeks of illness. For stronger diagnostic accuracy, IgM B. afzelii results should be considered alongside other Borrelia markers (e.g., B. burgdorferi sensu stricto, B. garinii, Osp proteins) and the patient’s clinical presentation. Summary The IgM B. afzelii marker helps detect early immune responses to a key European subspecies of Lyme disease. A positive result may point to a recent infection, especially when skin involvement is present, but equivocal or borderline results should be confirmed with repeat testing or additional Lyme panels. Together with clinical history and other antibody markers, this test contributes to a more accurate diagnosis of Lyme borreliosis.

IgM B. burgdorferi sensu stricto: Early Antibody Marker for Lyme Disease Overview The IgM B. burgdorferi sensu stricto (Bb ss) test detects early-stage antibodies against Borrelia burgdorferi sensu stricto, the primary bacterial species that causes Lyme disease in North America. Lyme borreliosis is a tick-borne infection that can affect the skin, joints, nervous system, and heart. The Role of IgM Antibodies IgM antibodies are among the immune system’s first responders to infection. In Lyme disease: IgM typically appears 1–2 weeks after a tick bite Peaks during the first month of infection Declines as the longer-lasting IgG response develops Detecting IgM antibodies against Borrelia burgdorferi sensu stricto can therefore indicate: A recent or early-stage infection (acute or early disseminated Lyme disease) Ongoing immune activity in patients with persistent symptoms Rarely, false-positive results or persistent IgM without IgG, which underscores the need for clinical correlation Clinical Significance A positive IgM response against Borrelia burgdorferi sensu stricto is a key diagnostic clue in early Lyme disease, particularly in patients with: Tick exposure in endemic regions Early Lyme symptoms such as erythema migrans (“bull’s-eye” rash), fever, fatigue, muscle aches, or headache Neurological signs (e.g., facial palsy, meningitis) or musculoskeletal symptoms (e.g., joint pain, early arthritis) that arise within weeks of infection If untreated, early Lyme infection can progress to Lyme arthritis, neuroborreliosis, or Lyme carditis. Early recognition through IgM testing supports timely treatment and reduces the risk of complications. Limitations and Considerations While IgM testing is valuable, results require cautious interpretation: False positives may occur due to cross-reactivity with other infections or autoimmune conditions Isolated IgM positivity without subsequent IgG conversion—especially beyond 6–8 weeks after symptom onset—may not reflect active infection Confirmatory testing with additional Borrelia antigens (e.g., Osp proteins) or co-infection panels improves diagnostic accuracy Summary The IgM B. burgdorferi sensu stricto test provides important insight into the early immune response to Lyme disease. A positive result suggests recent or current infection, but interpretation should always be based on clinical presentation, exposure history, and other laboratory findings. As part of the broader Lyme immunoserology panel, this marker helps guide earlier detection and management of Lyme disease.

IgM B. burgdorferi Antigen (AG) Test: Early Antibody Marker for Lyme Disease Overview The IgM B. burgdorferi Antigen (AG) test detects early-stage antibodies against Borrelia burgdorferi, the spirochete bacterium responsible for Lyme disease. Unlike subspecies- or protein-specific assays, this test measures IgM antibodies directed against a broader set of Borrelia antigens, improving sensitivity and making it a valuable tool in the early detection of Lyme borreliosis. The Role of IgM Antibodies IgM is the first class of antibodies produced by the immune system during infection. In Lyme disease: IgM typically appears 1–2 weeks after a tick bite Peaks during the first month of infection Declines as IgG antibodies become more dominant Measuring IgM against Borrelia antigens provides insight into a recent or active immune response, making it particularly useful in identifying early-stage infection. Clinical Significance A positive IgM response against B. burgdorferi antigens suggests a possible recent infection. This is especially relevant for patients with: Early Lyme symptoms such as erythema migrans (bull’s-eye rash), fever, fatigue, headache, or muscle aches Neurological manifestations including cranial neuritis, meningitis, or cognitive changes Musculoskeletal involvement such as migratory joint pain or early Lyme arthritis Because IgM reflects the early immune response, this marker can support recognition of Lyme disease before complications such as arthritis, carditis, or neuroborreliosis develop. Limitations and Considerations False positives may occur due to cross-reactivity with other infections or autoimmune conditions Isolated IgM positivity without subsequent IgG development, particularly beyond 6–8 weeks of symptoms, may not indicate active infection Persistent IgM antibodies can be detected in some individuals even after treatment, making clinical context essential Additional testing with subspecies markers (B. afzelii, B. garinii) or antibodies to Outer Surface Proteins (OspA, OspC, OspE) can improve diagnostic accuracy when interpreted alongside IgM AG results Broader Context in Lyme Testing Traditional Lyme serology, such as ELISA and Western Blot, measures antibodies to mixtures of Borrelia proteins. While sensitive, these methods may lack specificity. Newer multi-antigen ELISA and next-generation immunoserology approaches combine cultured Borrelia antigens with in vivo–expressed proteins, allowing for more precise differentiation between Lyme disease and other conditions. The IgM B. burgdorferi AG test remains a foundational early marker within this broader testing strategy. Summary The IgM B. burgdorferi Antigen (AG) test captures the body’s early antibody response to Lyme disease. A positive result may support the diagnosis of a recent or ongoing infection, but it should never be interpreted in isolation. Results are most informative when combined with clinical history, symptom timing, IgG antibodies, and confirmatory testing. As part of a comprehensive serologic panel, this marker plays a key role in the early identification and management of Lyme disease, helping to prevent progression to later-stage complications.

Overview The IgM B. garinii test detects early antibodies against Borrelia garinii, a key subspecies within the Borrelia burgdorferi sensu lato complex that causes Lyme disease. While B. burgdorferi sensu stricto is the primary agent in North America, B. garinii is most common in Europe and parts of Asia, where it is strongly associated with neurological forms of Lyme disease (neuroborreliosis). The Role of IgM Antibodies IgM is the first antibody class produced by the immune system during infection. In Lyme disease: IgM antibodies typically appear 1–3 weeks after a tick bite They peak in the first month of infection Often decline as IgG antibodies develop Detection of IgM antibodies specific to B. garinii suggests a recent immune response and supports early recognition of infection, particularly in neurological cases. Clinical Significance of B. garinii Borrelia garinii is notable for its neurotropism (tendency to affect the nervous system). Clinical associations include: Lymphocytic meningitis (headache, neck stiffness, fever) Cranial neuritis, particularly facial palsy Radiculoneuritis (nerve pain, tingling, or weakness) Cognitive or memory disturbances in disseminated infection Although primarily linked with neuroborreliosis, B. garinii can occasionally present with joint or cardiac involvement. A positive IgM B. garinii result is therefore especially relevant in patients with neurological symptoms after tick exposure in endemic areas. Limitations and Considerations False positives can occur due to cross-reactivity Timing matters: best interpreted within the first month Beyond 6–8 weeks, isolated IgM without IgG is less reliable Geography matters: highly relevant in Europe/Asia, less so in North America unless travel is involved Confirmatory testing (IgG antibodies, Osp proteins, subspecies assays) improves accuracy Broader Context in Lyme Testing Different Borrelia subspecies drive different disease patterns: B. afzelii → mainly skin involvement B. burgdorferi sensu stricto → joint disease B. garinii → neurological involvement Including IgM B. garinii in European Lyme panels increases diagnostic precision by capturing the neurological spectrum of the disease. Summary The IgM B. garinii test identifies early antibody responses to a subspecies strongly linked to neurological Lyme disease in Europe and Asia. A positive result may reflect a recent or ongoing infection, especially in patients with neurological symptoms following tick exposure. Because cross-reactivity and false positives are possible, results should always be interpreted with clinical history, geography, and confirmatory Lyme testing.

Overview The IgM B. miyamotoi test measures early antibodies against Borrelia miyamotoi, a spirochete related to the Borrelia burgdorferi sensu lato complex but classified within the relapsing fever group of Borrelia, rather than the classical Lyme-associated species. First identified in Japan in 1995, B. miyamotoi is now recognized in North America, Europe, and Asia as an emerging tick-borne pathogen transmitted by the same Ixodes ticks that spread Lyme disease. The Role of IgM Antibodies IgM antibodies are part of the immune system’s first response to infection. In B. miyamotoi disease (BMD), IgM typically becomes detectable within days to weeks of symptom onset. Since BMD often presents as an acute, flu-like illness with relapsing fever episodes, early IgM detection is an important indicator of recent or ongoing infection. Clinical Significance of B. miyamotoi Borrelia miyamotoi causes Borrelia miyamotoi disease (BMD), which shares clinical features with both Lyme disease and tick-borne relapsing fever. Characteristic findings include: Flu-like symptoms: fever, chills, fatigue, muscle aches, headache Relapsing fever: recurrent febrile episodes, typical of relapsing fever Borrelia Neurological complications, such as meningoencephalitis, especially in immunocompromised patients Absence of erythema migrans: unlike Lyme disease, BMD usually does not present with the bull’s-eye rash Because BMD overlaps with other tick-borne illnesses but lacks hallmark Lyme signs, IgM testing helps clinicians suspect and identify this distinct infection. Limitations and Considerations Cross-reactivity: Antibodies may react with Lyme-related Borrelia antigens; specific testing helps distinguish BMD from Lyme disease. Timing: IgM is most informative early; in longer illness courses, IgG testing may be more reliable. Emerging recognition: As a relatively new pathogen, clinical experience and diagnostic access are more limited than for classical Lyme. Geographic relevance: Positive results are most meaningful where Ixodes ticks are common (North America, Europe, Asia), and must be interpreted in light of exposure history. Broader Context in Tick-Borne Illness The discovery of B. miyamotoi underscores that tick-borne diseases extend beyond Lyme disease alone. Ixodes ticks can transmit Borrelia burgdorferi, Anaplasma, Babesia, and B. miyamotoi, making co-infections possible and often complicating clinical presentation. Including IgM B. miyamotoi testing alongside other tick-borne panels provides a more complete assessment when evaluating patients with fever, relapsing symptoms, or neurological issues after tick exposure. Summary The IgM B. miyamotoi test detects early antibody responses to a relapsing fever–type Borrelia increasingly recognized as an emerging human pathogen. A positive result suggests a recent or active infection, typically presenting as relapsing fever with flu-like illness, and in some cases, neurological involvement. Because B. miyamotoi disease differs clinically from classical Lyme borreliosis, results should always be interpreted in the context of symptoms, exposure history, and confirmatory testing for other tick-borne pathogens.

Overview The IgM Babesia test detects early antibodies against Babesia species, a group of tick-borne protozoan parasites that infect red blood cells. Unlike Lyme disease, caused by Borrelia bacteria, babesiosis is a malaria-like illness most commonly linked to Babesia microti in North America and Babesia divergens or Babesia venatorum in Europe. By destroying red blood cells, Babesia can cause illness ranging from mild fatigue to life-threatening infection in at-risk patients. The Role of IgM Antibodies IgM antibodies are the first line of immune defense against infection. In babesiosis, IgM typically appears within 1–2 weeks of exposure, serving as an early marker of recent or acute infection. Because Babesia parasites can persist in circulating red blood cells, IgM testing helps identify cases early, sometimes before IgG antibodies or confirmatory findings are detectable. Clinical Significance of Babesia Infection The severity of babesiosis varies widely depending on patient age, immune status, and splenic function. Clinical features include: Flu-like illness: fever, chills, sweats, headache, fatigue Hemolytic anemia: pallor, jaundice, or shortness of breath from red blood cell destruction Splenomegaly: enlarged spleen in more advanced or severe cases Severe disease: immunocompromised patients, the elderly, or those without a spleen are at highest risk for multi-organ failure, high parasite burden, and death if untreated Early detection by IgM markers is particularly important in these vulnerable groups. Limitations and Considerations Cross-reactivity: IgM antibodies may show low-level reactivity or persist, limiting specificity. Confirmatory testing: Diagnosis is generally supported by blood smear microscopy, PCR, or IgG testing. Co-infections: Because Ixodes ticks can also carry Borrelia (Lyme) and Anaplasma, co-infections are common and may complicate disease presentation and management. Geographic distribution: B. microti predominates in the Northeastern and upper Midwestern U.S., while severe B. divergens infections are more typical in Europe. Broader Context in Tick-Borne Disease Babesiosis fits into the broader spectrum of tick-borne illnesses, often occurring alongside Lyme disease from the same tick bite. While Lyme primarily targets connective tissues and nerves, Babesia destroys red blood cells, leading to hemolytic complications. Recognition of IgM Babesia is critical for distinguishing co-infections, since treatment requires antiparasitic therapy (e.g., atovaquone plus azithromycin or clindamycin plus quinine in severe cases) rather than antibiotics alone. Summary The IgM Babesia test identifies the body’s early immune response to infection with Babesia parasites. A positive result suggests recent or active babesiosis, which may range from mild flu-like illness to severe, life-threatening disease in high-risk individuals. Because co-infections with Lyme disease and other tick-borne pathogens are common, IgM results should always be interpreted in the context of symptoms, confirmatory testing, and exposure risk, helping clinicians recognize babesiosis as a distinct and important tick-borne infection requiring targeted therapy.

The IgM Bartonella test detects early antibodies against Bartonella species, a group of bacteria transmitted by ticks, fleas, lice, or scratches from infected animals (especially cats). The most common human pathogens are Bartonella henselae and Bartonella quintana, which can cause cat scratch disease, trench fever, or tick-borne bartonellosis. In some cases, Bartonella infections may contribute to chronic fatigue, neurological issues, or joint pain, especially when co-infections with Lyme disease or Babesia are present. What IgM Bartonella Means IgM antibodies are the body’s first response to infection and usually appear within the first 1–3 weeks after exposure. A positive IgM Bartonella result suggests a recent or active infection. Because IgM may decline over time, this test is most reliable during the early stages of infection. Clinical Importance Testing for IgM Bartonella may be most useful in patients who have: Acute symptoms such as fever, swollen lymph nodes, fatigue, or muscle aches Neurological problems like headaches, neuropathy, or cognitive changes Skin or eye inflammation sometimes linked to Bartonella infection Recent tick, flea, or cat exposure in areas where Bartonella is known to circulate Patient Takeaway A positive IgM Bartonella result suggests that your immune system is currently fighting or has very recently fought a Bartonella infection. However, IgM antibodies alone are not enough to confirm the diagnosis, since false positives and cross-reactions can occur. Your healthcare provider will interpret this result alongside your symptoms, exposure history, and other tests (such as IgG, PCR, or culture-based methods). If your IgM result is equivocal (borderline), antibody levels are near the cutoff and the finding is uncertain. In these cases, repeat or confirmatory testing is often recommended.

Overview The IgM Ehrlichia test detects early antibody responses to infection with Ehrlichia species, tick-borne intracellular bacteria that infect white blood cells and cause ehrlichiosis. The main human pathogens are Ehrlichia chaffeensis (causing human monocytic ehrlichiosis, HME) and Ehrlichia ewingii. Ehrlichiosis is most common in the southeastern and south-central United States, but cases are also reported in other tick-endemic regions worldwide. The Role of IgM Antibodies IgM antibodies are the earliest detectable immune response, usually appearing within the first 1–2 weeks of illness. In ehrlichiosis, detection of IgM can suggest recent or acute infection, particularly when consistent symptoms are present. However, IgM alone is not a definitive marker since low levels may appear late and cross-reactivity with other infections is possible. Clinical Significance of Ehrlichiosis Ehrlichiosis is an acute febrile illness ranging from mild to life-threatening. Symptoms generally develop 1–2 weeks after a tick bite, and may include: Flu-like illness: fever, chills, severe headache, muscle aches, fatigue Gastrointestinal symptoms: nausea, vomiting, abdominal pain Neurological findings: confusion, meningitis, seizures in severe cases Laboratory abnormalities: leukopenia, thrombocytopenia, and elevated liver enzymes Patients at highest risk for severe disease include older adults, immunocompromised individuals, and those with delayed treatment, who may develop respiratory failure, bleeding disorders, or multi-organ involvement. Limitations and Considerations Early testing challenge: IgM may be absent in the first few days despite active infection, reinforcing the importance of clinical suspicion. False positives: Cross-reactivity with antibodies from other tick-borne pathogens may lead to nonspecific IgM results. Confirmatory testing: PCR during the acute phase or IgG seroconversion in paired samples offers stronger diagnostic evidence. Treatment urgency: Because ehrlichiosis can progress rapidly, empiric therapy with doxycycline is recommended without waiting for test confirmation. Broader Context in Tick-Borne Disease Ehrlichiosis is one of several serious infections transmitted by the lone star tick (Amblyomma americanum) and related species. Co-infection with Lyme disease, Anaplasma, or Babesia is possible, and overlapping symptoms may complicate diagnosis. Including IgM Ehrlichia testing within a tick-borne disease panel allows clinicians to identify and manage these complex cases more effectively. Summary The IgM Ehrlichia marker identifies early immune responses to a potentially severe tick-borne illness. A positive result suggests recent or acute infection, often accompanied by fever, abnormal blood counts, and systemic symptoms. Because ehrlichiosis can progress quickly if untreated, results must always be interpreted in conjunction with clinical findings, confirmatory testing, and timely medical care.

Overview The IgM Immunodominant C6 (IR6) test detects early antibodies against the conserved C6 peptide, a 26–amino acid sequence from the invariable region (IR6) of VlsE, the variable surface antigen in Borrelia burgdorferi sensu lato. While VlsE undergoes domain variation to evade the immune system, the IR6 region remains highly conserved across Lyme-causing subspecies (B. burgdorferi sensu stricto, B. afzelii, B. garinii). This conservation makes C6-based assays valuable broad-spectrum markers in Lyme serology. Why IgM to C6 Matters Early signal of infection: IgM antibodies are the first to rise after exposure, and anti-C6 IgM can appear within 1–3 weeks of a tick bite, indicating early or recent infection. Cross-subspp coverage: Because the C6 epitope is conserved, the assay can detect immune responses across diverse Borrelia subspecies in North America, Europe, and parts of Asia. Diagnostic utility: Evaluations of C6 ELISA show high sensitivity in acute infection (increasing into convalescence) and strong specificity, supporting its rule-in value when combined with compatible symptoms and exposure risk. Clinical Significance A positive IgM C6 suggests an early immune response to Lyme borreliosis, particularly valuable for patients with: Early localized or disseminated disease: erythema migrans, fever, headache, myalgia, fatigue Neurological presentations: meningitis, cranial neuritis, radiculoneuritis Musculoskeletal involvement: migratory arthralgias or evolving arthritis Because C6 can be measured quantitatively, serial testing may support follow-up, though antibody kinetics vary and serology should not be used alone to monitor treatment response. Limitations and Interpretation Caveats Timing: IgM is most informative within the first month; isolated IgM beyond 6–8 weeks without IgG warrants caution (may reflect non-specific reactivity or past exposure). Cross-reactivity: Though designed for specificity, occasional reactivity occurs (e.g., autoimmune triggers or other Borrelia species). Notably, C6 reactivity has been described in Borrelia miyamotoi (a relapsing fever–group spirochete). No subspecies resolution: C6 reflects pan-Borrelia exposure but does not identify the infecting strain or stage of disease. Clinical context required: A positive C6 IgM alone does not confirm active Lyme. Integration with exposure history, symptoms, exam findings, confirmatory markers (VlsE/whole-cell EIAs, immunoblots, Osp proteins, subspecies-specific antigens), and co-infection assessment (Babesia, Anaplasma/Ehrlichia, Bartonella) is essential. Role in Modern Lyme Testing C6 assays are increasingly used in modified two-tier Lyme testing algorithms, valued for their broad coverage and strong analytic performance. In multi-antigen ELISA panels, IgM C6 complements other markers such as OspC, VlsE/DbpA, and subspecies-specific assays, enhancing early detection while maintaining high specificity across the clinical spectrum. Summary The IgM Immunodominant C6 marker is a conserved, early-phase Lyme serology tool that captures recent immune responses across major Borrelia subspecies. It offers strong diagnostic value in acute disease but requires careful interpretation, particularly when IgM is isolated or when cross-reactivity is considered. Most powerful when paired with compatible symptoms, exposure history, and complementary serology, IgM C6 serves as a core element of modern multi-antigen Lyme testing strategies.

Overview The IgM LFA Antigen + CK10 test looks at two parts of the immune system: how your body responds to infections in the short term and whether it may be reacting against its own tissues (autoimmunity). It does this by measuring IgM antibodies (early infection fighters) and antibodies against Cytokeratin 10 (CK10), a protein found in the skin and other epithelial tissues. What IgM Antibodies Tell Us IgM is the first antibody type your body produces when it fights off a new infection. Finding IgM in this test can signal a recent or ongoing infection, such as from a virus, bacteria, or parasite. Normally, IgM is later replaced by longer-lasting IgG antibodies. If IgM stays high for too long, it may point to continued immune activity or a possible autoimmune process. What CK10 Antibodies Mean CK10 is a protein that helps give structure to skin cells. Sometimes the immune system mistakenly produces antibodies against CK10, which may happen in conditions such as: Autoimmune skin diseases (like pemphigus or pemphigoid) Psoriasis or chronic skin inflammation Conditions where the skin barrier is damaged and the immune system targets exposed proteins These antibodies can be a clue that the immune system is mistakenly attacking the body’s own tissues. Why Combining IgM and CK10 Matters By looking at both infection-related IgM and CK10 autoantibodies, this test helps healthcare providers and researchers: Differentiate between symptoms caused by infections vs. autoimmunity Detect immune activity early, before long-term tissue damage occurs Explore how infections might trigger autoimmune reactions, which is a growing area of research in chronic inflammatory and autoimmune diseases Key Takeaways IgM antibodies help show if your body is currently fighting an infection. CK10 antibodies may suggest the immune system is attacking skin or epithelial cells. Together, these results give a clearer picture of whether symptoms are driven by infection, autoimmunity, or a combination of both.

IgM Outer Surface Protein A + C (OspA + OspC) The IgM OspA + OspC test detects early immune responses to Borrelia burgdorferi, the bacteria responsible for Lyme disease. It looks for IgM antibodies against two key surface proteins: OspC (Outer Surface Protein C): Produced in the early stages of infection. OspA (Outer Surface Protein A): More often associated with later or persistent infection. Because Borrelia expresses these proteins at different points in its life cycle, testing for both can provide a broader picture of the stage and progression of Lyme disease. What the Results Mean OspC IgM antibodies: Typically appear within 2–3 weeks after a tick bite, making them a strong marker for recent Lyme infection. OspA IgM antibodies: More often linked with later or persistent disease, and sometimes with chronic or autoimmune-like manifestations of Lyme. When considered together, OspA and OspC testing helps clinicians estimate where a patient may be along the Lyme disease timeline. Clinical Importance This test may be most helpful for patients who present with: Early Lyme symptoms such as fever, rash (erythema migrans), fatigue, headache, or muscle aches Neurological involvement including facial palsy, meningitis-like symptoms, or nerve pain Joint pain or swelling that develops weeks to months after exposure Documented tick bites or exposure in areas where Lyme disease is common Limitations IgM reliability is time-sensitive: IgM is most useful in the early weeks of infection. Isolated IgM positivity months later may not indicate active infection. False positives can occur due to cross-reactivity with other bacterial or viral infections. Confirmatory testing is standard: Additional markers such as IgG antibodies, VlsE/C6 peptide, or multi-antigen panels are often used to strengthen diagnostic accuracy. Patient Takeaway A positive IgM OspA + OspC test means your immune system is producing early antibodies against Borrelia, suggesting possible recent or ongoing exposure to the bacteria that causes Lyme disease. However, this test alone does not confirm Lyme disease. Your doctor will always interpret the results in the context of: Your symptoms Tick exposure history Other Lyme disease test results If your test is reported as equivocal (borderline), it means antibody levels are close to the cutoff and not clearly positive or negative. In these cases, your provider may recommend repeat testing or additional confirmatory panels.

The IgM OspE test detects early antibodies against Outer Surface Protein E (OspE) of Borrelia burgdorferi, the bacterium responsible for Lyme disease. OspE belongs to the Erp (OspE-related proteins) family, which helps Borrelia survive in the human bloodstream by binding to factor H, a host protein that protects the bacteria from complement-mediated killing. What IgM OspE Means IgM antibodies usually appear within the first 1–3 weeks after infection, making this test useful for detecting early or recent exposure to Borrelia. A positive IgM OspE result suggests that the immune system is actively responding to Borrelia at the early stage of infection. Because OspE is associated with immune evasion, antibody detection may indicate Borrelia dissemination in the bloodstream. Clinical Importance Testing for IgM OspE can be helpful in patients who have: Early Lyme symptoms such as fever, rash, fatigue, headache, or muscle aches Neurological or joint issues appearing shortly after suspected infection Recent tick exposure in areas where Lyme disease is common Unexplained immune activation that overlaps with Lyme-like presentations Patient Takeaway A positive IgM OspE result suggests your immune system has recently recognized Borrelia, pointing to a new or active infection. However, since IgM testing can sometimes produce false positives or cross-react with other infections, it is not considered diagnostic on its own. Your healthcare provider will interpret the result alongside your symptoms, history of tick exposure, and other Lyme disease markers (such as OspC, OspA, or VlsE/C6). If your IgM OspE test result is equivocal (borderline), antibody levels are near the cutoff and the finding is uncertain. In such cases, repeat or confirmatory testing is usually recommended.

Overview The IgM Variable Major Protein E (VmpE) test detects early antibodies against a highly adaptable surface protein produced by Borrelia burgdorferi, the bacterium that causes Lyme disease. VmpE belongs to a family of variable major proteins (Vmps) that the bacteria switch on and off to escape immune detection, a process known as antigenic variation. Because of this constant shifting, VmpE is linked to Borrelia’s ability to persist and cause relapsing or chronic forms of infection. Understanding VmpE and the Immune Response Immune evasion: By rearranging its genes, Borrelia changes VmpE’s structure, escaping recognition by pre-existing antibodies. Role in persistence: This variation allows Borrelia to survive for long periods in the host, even after initial immune clearance. IgM recognition: Detecting IgM antibodies to VmpE indicates the immune system is actively responding to these variable proteins, usually in the early weeks of infection or in cases of ongoing immune activation. IgM Response to VmpE Appears within 1–3 weeks after a tick bite, often before IgG antibodies are detected. Effective in the early neutralization of infection but may persist when Borrelia continues producing new variants. Complements markers such as OspC and VlsE, broadening diagnostic insight into both early and persistent Lyme presentations. Clinical and Research Relevance Clinical use: May help support diagnosis in early Lyme disease, in suspected persistent infection, or when symptoms overlap with autoimmune-like conditions linked to chronic immune activation. Research value: Offers insight into how Borrelia uses antigenic variation to survive, why some patients may develop relapsing or chronic symptoms, and whether conserved VmpE regions might hold future vaccine potential. Limitations & Considerations Best early: IgM detection is most informative in the early weeks after infection. Caution later: Isolated IgM beyond 6–8 weeks may not indicate active infection. False positives: Cross-reactivity with other infections can occur. Confirmation needed: Other tests (IgG, VlsE/C6, multi-antigen panels) are often used alongside IgM VmpE for diagnostic accuracy. Summary The IgM VmpE test provides insight into the body’s early immune response against a variable protein used by Borrelia to escape detection and persist in the host. A positive result may suggest recent or ongoing infection, but interpretation requires clinical context, exposure history, and other supportive test results. If results are equivocal (borderline), antibody levels are near the cut-off and uncertain — this may indicate very early infection or a nonspecific immune reaction; repeat or confirmatory testing is usually recommended.