IgA (immunoglobulin A) is a group representing approximately 15% of the antibodies present in the blood. They are also found in saliva, tears, respiratory and gastric secretions and breast milk. IgA provides protection against respiratory mucous membrane (sinus and lung) infections and gastrointestinal (stomach and intestine) infections. Transmitted by the mother through breastfeeding, IgA protects the newborn’s digestive tract. IgA levels are interpreted in light of IgG and IgM, the other two main classes of antibodies.
Isolated decreases in IgA are very rare. Simultaneously low levels of IgA, IgG and IgM are usually due to conditions that negatively impact their production (immunosuppressive drugs, diabetes complications or kidney disease, etc.) or that increase their loss through the kidneys (nephrotic syndrome), intestines (exudative enteropathy) or skin (burns). Uncontrolled production of another class of immunoglobulins such as IgG or IgM (multiple myeloma) sometimes causes a significant decrease in the synthesis of the other classes (such as IgA).
High levels of IgA occur in mucosal infections, autoimmune diseases and chronic inflammatory conditions such as rheumatoid arthritis, alcoholic cirrhosis, etc. Specific increases in IgA are rare (IgA multiple myeloma).