Anti-C1q autoantibodies are indicative for lupus nephritis, but can also be found in other conditions and inflammatory diseases.

Circulating immune complexes can be demonstrated in rheumatic, infectious, and neoplastic diseases, as well as most immunologically mediated illnesses (inflammatory bowel disease, thrombotic thrombocytopenic purpura). Complement is part of the innate immune system. Its major function is recognition and elimination of pathogens. Complement activity plays also an important role in the pathogenesis of systemic autoimmune diseases.

Immunofixation electrophoresis or immunosubtraction capillary electrophoresis identifies the type of immunoglobulin protein(s) present as monoclonal bands on a protein electrophoresis pattern. Typically, this testing determines the presence and type of monoclonal proteins (e.g., IgG kappa).

Immunoglobulin A (IgA), one of the five primary immunoglobulins, plays a pivotal role in mucosal homeostasis in the gastrointestinal, respiratory, and genitourinary tracts, functioning as the dominant antibody of immunity in this role.

Total IgA (Immunoglobulin A), expressed in milligrams per deciliter (mg/dL), is a crucial marker in clinical immunology representing the predominant immunoglobulin class in mucosal secretions and the second most abundant immunoglobulin in serum. This glycoprotein plays a pivotal role in mucosal immunity, offering a primary line of defense against pathogens at mucosal surfaces, including the gastrointestinal, respiratory, and genitourinary tracts. Normal levels of Total IgA in the blood vary based on age and individual health conditions but typically range from 70 to 400 mg/dL in adults.

Immunoglobulin D (IgD) is an antibody isotype that makes up about 1% of proteins in the plasma membranes of immature B-lymphocytes where it is usually coexpressed with another cell surface antibody called IgM.

Remains in the bloodstream to fight bacteria. Functions mainly as an antigen receptor on B cells that have not been exposed to antigens. It has been shown to activate basophils and mast cells to produce antimicrobial factors.

Immunoglobulin E (IgE) is a key antibody in the immune system, crucial for diagnosing and managing allergies. Testing for IgE is important for identifying specific allergens causing allergic reactions, which can range from mild symptoms like sneezing to severe, potentially life-threatening conditions like anaphylaxis. Measuring IgE levels helps in creating personalized treatment plans, including medication and immunotherapy. It's also used to monitor the effectiveness of allergy treatments and assess the severity of chronic conditions like asthma. Elevated IgE levels can indicate broader immune system issues, making it a valuable tool in immunological assessments. With allergies becoming more common, IgE testing is increasingly important in healthcare, aiding in better patient care in allergy and immunology.

Immunoglobulin E (IgE) are antibodies produced by the immune system. 

IgE antibodies are found in the lungs, skin, and mucous membranes. They cause the body to react against foreign substances such as pollen, fungus spores, and animal dander. They are also involved in allergic reactions to milk, some medicines, and some poisons.

In the blood of healthy people, IgE antibodies make up less than 0.001% of all immunoglobulins. These IgE antibodies are key in triggering allergic responses when people sensitive to allergens come into contact with them.

Structurally, IgE resembles other antibodies, having two light chains and two heavy chains. The heavy chains have a special region that determines the antibody's specificity to antigens. Measuring IgE levels is clinically significant mainly because of its role in allergic reactions, even though IgE myeloma is a very rare condition.

The most abundant immunoglobulin in human serum is immunoglobulin G (IgG) (approximately 80% of the total). IgG protein is comprised of molecules of 4 subclasses designated IgG1 through IgG4. Each subclass contains molecules with a structurally unique gamma heavy chain. Of total IgG, approximately 65% is IgG1, 25% is IgG2, 6% is IgG3, and 4% is IgG4. Molecules of different IgG subclasses have somewhat different biologic properties (eg, complement fixing ability and binding to phagocytic cells), which are determined by structural differences in gamma heavy chains. Clinical interest in IgG subclasses concerns potential immunodeficiencies (eg, subclass deficiencies) and IgG4-related diseases (eg, IgG4 elevations). The IgG subclass assay (IGGS / IgG Subclasses, Serum) is best for deficiency testing, and the IgG4 assay (IGGS4 / Immunoglobulin Subclass IgG4, Serum) is best for IgG4-related disease testing.

Immunoglobulin M (IgM), which is found mainly in the blood and lymph fluid, is the first antibody to be made by the body to fight a new infection. Expressed on the surface of B cells (monomer) and in a secreted form (pentamer) with very high avidity (forms multiple binding sites with antigen). Eliminates pathogens in the early stages of B-cell mediated (humoral) immunity before there is sufficient IgG. 

Immunoglobulin M (IgM), which is found mainly in the blood and lymph fluid, is the first antibody to be made by the body to fight a new infection. Expressed on the surface of B cells (monomer) and in a secreted form (pentamer) with very high avidity (forms multiple binding sites with antigen). Eliminates pathogens in the early stages of B-cell mediated (humoral) immunity before there is sufficient IgG. 

IgG immunoglobulins are composed of four subtypes named IgG1, IgG2, IgG3 and IgG4. Each subclass is present in the serum in different concentrations, varies with age, and has different roles for immune response. Abnormal levels of one or more subclasses may be associated with certain conditions.

This marker helps to evaluate sinopulmonary infections, asthma; immunotherapy hyposensitization; and allergies.

Indican is an indole produced when bacteria in the intestine act on the amino acid, tryptophan. Most indoles are excreted in the feces. The remainder is absorbed, metabolized by the liver, and excreted as indicanin the urine.

Indican is an indole produced when bacteria in the intestine act on the amino acid, tryptophan. Most indoles are excreted in the feces.

The remainder is absorbed, metabolized by the liver, and excreted as indicanin the urine.

Accumulated levels of Indican in the urine may suggest gastrointestinal dysbiosis or malabsorption.

Indican is a byproduct of tryptophan putrefaction by microbes in the gut. Accumulated levels of indican in the urine suggest higher levels of tryptophan putrefaction from gastrointestinal dysbiosis or malabsorption.

Production of indican occurs when tryptophan creates indoles in the colon. No other endogenous indoles are metabolized in this way, so when we see indican in the urine, it is directly related to gut production and a direct reflection of gut health. When there is concern of dysbiosis, there may be poor metabolism of sex hormones (including estrogen) along with chronic low-grade inflammation that can impact cortisol production and metabolism.

Indole is a byproduct of the microbial degradation of tryptophan that can be utilized in a variety of ways in the gut microbiome. Indole can bind to serotonin receptors in order to regulate behavior, gut motility, and food intake, and it can support immune and intestinal health by interacting with gut microbes, scavenging free radicals, and increasing the expression of xenobiotic-metabolizing enzymes like cytochrome P450. Indole also functions as a signaling molecule that may be increased during latent infections. Indole production must be balanced, as too much indole may produce unwanted changes in mood or cognition, yet insufficient indole production may damage the gut barrier.

Indoleacetic acid (IAA), or indole-3-acetate, is produced by the bacterial fermentation of the amino acid tryptophan.

IAA can be formed from several common gut microbes such as Clostridia species, Escherichia coli, and Saccharomyces species.

- A product of tryptophan fermentation. If elevated, decrease protein intake and address digestion and GI issues. Bacteroides, Clostridia, and E. coli ferment tryptophan to produced indoleacetic acid.

- It has been found elevated in liver disease, ASD, and cancer, and has been noted as a marker of microbial activity.

- Indoleacetic acid can be degraded by Bacillus subtilis, or Pseudomonas aeruginosa.

- Indoleacetic acid has been found in many foods, such as lettuce, cherry tomato, Chinese bayberry, and okra.

Indoleacetic acid (IAA), or indole-3-acetate, is produced by the bacterial fermentation of the amino acid tryptophan.

IAA can be formed from several common gut microbes such as Clostridia species, Escherichia coli, and Saccharomyces species.

Produced from bacterial degradation of unabsorbed tryptophan.