IgG Subclass Deficiency
What Is the IgG Subclass Deficiency Panel?
The IgG Subclass Deficiency Panel is a blood test that measures the levels of the four IgG (Immunoglobulin G) subclasses:
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IgG1
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IgG2
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IgG3
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IgG4
These subclasses are all part of the IgG antibody family, which plays a crucial role in your immune system's ability to recognize and fight off bacteria, viruses, and other pathogens. While total IgG may appear normal, an individual may still be deficient in one or more subclasses—this is known as an IgG subclass deficiency.
Why Is This Test Ordered?
This panel is typically ordered if you:
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Have frequent or recurrent infections, especially of the sinuses, lungs, or ears
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Show signs of a weakened immune system
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Have a normal total IgG level but suspected immune dysfunction
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Are being evaluated for a primary immunodeficiency disorder (PID)
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Are being monitored for certain autoimmune or inflammatory conditions
What Each IgG Subclass Does
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IgG1: The most abundant subclass, important for response to protein antigens (like tetanus or diphtheria).
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IgG2: Plays a key role in defense against bacterial infections, especially encapsulated bacteria (e.g., Streptococcus pneumoniae).
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IgG3: Effective against viral antigens; has strong pro-inflammatory properties.
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IgG4: Involved in long-term or chronic antigen exposure and can be elevated in some autoimmune and allergic conditions.
What Does an IgG Subclass Deficiency Mean?
A deficiency in one or more IgG subclasses may lead to increased susceptibility to infections, even if the total IgG level is within the normal range.
Common Patterns of Deficiency:
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IgG2 Deficiency: Often associated with recurrent bacterial sinus or lung infections, especially in children.
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IgG3 Deficiency: May be linked to chronic respiratory infections or viral susceptibility.
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IgG1 Deficiency: Can result in broader immune dysfunction, sometimes in combination with other deficiencies.
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Selective IgG4 Deficiency: Less well understood, but may co-exist with other immune abnormalities.
Symptoms of IgG Subclass Deficiency
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Frequent sinus, ear, or respiratory infections
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Poor response to vaccines
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Chronic cough or bronchitis
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Fatigue due to repeated illnesses
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In children: failure to thrive or delayed growth due to illness
Diagnosis and Next Steps
If your IgG subclass levels are low, your healthcare provider may:
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Review your infection history
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Order pneumococcal antibody titers to assess vaccine response
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Test total immunoglobulin levels (IgG, IgA, IgM)
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Consider referral to an immunologist
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Recommend immunoglobulin replacement therapy (IVIG or SCIG) in severe cases
Summary
The IgG Subclass Deficiency Panel evaluates whether your immune system is producing adequate levels of each IgG subclass. A deficiency can explain frequent infections and guide further testing or treatment. Even if total IgG is normal, subclass imbalances can impact immune protection. This panel plays a key role in identifying hidden immune deficiencies and improving long-term infection management.
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Biomarkers included in this panel:
IgG is a combination of four slightly different types of IgG called IgG subclasses: IgG1, IgG2, IgG3 and IgG4. When one or more of these subclasses is persistently low and total IgG is normal, a subclass deficiency is present.
Learn moreIgG is a combination of four slightly different types of IgG called IgG subclasses: IgG1, IgG2, IgG3 and IgG4. When one or more of these subclasses is persistently low and total IgG is normal, a subclass deficiency is present.
Learn moreIgG is a combination of four slightly different types of IgG called IgG subclasses: IgG1, IgG2, IgG3 and IgG4. When one or more of these subclasses is persistently low and total IgG is normal, a subclass deficiency is present.
Learn moreIgG is a combination of four slightly different types of IgG called IgG subclasses: IgG1, IgG2, IgG3 and IgG4. When one or more of these subclasses is persistently low and total IgG is normal, a subclass deficiency is present.
Learn more