IgA

IgA or Immunoglobulin A is an antibody that plays a crucial role in the immune system's function in the mucous membranes. The amount of IgA produced in association with mucosal membranes is greater than all other types of antibody combined. In absolute terms, between three and five grams are secreted into the intestinal lumen each day. This represents up to 15% of total immunoglobulins produced throughout the body.

Function

IgA has two subclasses (IgA1 and IgA2) and can be produced as a monomeric as well as a dimeric form. The IgA dimeric form is the most prevalent and is also called secretory IgA (sIgA). sIgA is the main immunoglobulin found in mucous secretions, including tears, saliva, sweat, colostrum and secretions from the genitourinary tract, gastrointestinal tract, prostate and respiratory epithelium. It is also found in small amounts in blood.

Clinical significance

Deficiency of IgA is the most common immunodeficiency. It is defined as a serum IgA level below 7 mg/dL in a patient older than 4 years of age, in the presence of normal levels of other immunoglobulin isotypes. Most individuals with IgA deficiency remain healthy and symptom-free, but some may develop recurrent infections, allergies, and autoimmune diseases.

See also

• Immunoglobulin
• Antibody
• Immune system
• Mucous membrane

References

IgA Resources
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