Immunoglobulin A (IgA) Most Popular

Test Highlight

Clinical Use

• Diagnose IgA deficiencies

• Determine etiology of recurrent infections

• Diagnose infection

• Diagnose inflammation

• Diagnose IgA monoclonal gammopathy

Clinical Background

IgA is the first line of defense for the majority of infections at mucosal surfaces and consists of 2 subclasses. IgA1 is the dominant subclass, accounting for 80% to 90% of total serum IgA and greater than half of the IgA in secretions such as milk, saliva, and tears. IgA2, on the other hand, is more concentrated in secretions than in blood. IgA2 is more resistant to proteolytic cleavage and may be more functionally active than IgA1.

IgA deficiency is the most prevalent isotype deficiency, occurring in 1/400 to 1/700 individuals. Many patients with IgA deficiency are asymptomatic, while others may develop allergic disease, repeated sinopulmonary or gastroenterologic infections, and/or autoimmune disease. Individuals with complete absence of IgA (<5 mg/dL) may develop autoantibodies to IgA after blood or intravenous immunoglobulin infusions and may experience anaphylaxis on repeat exposure. 

Elevated serum IgA levels are associated with infection, inflammation, or IgA monoclonal gammopathy.