Immunoglobulin A (IgA) Deficiency
March 17th, 2010 by The Doc
Immunoglobulin A (IgA) is the most prevalent antibody found in secretions (tears, saliva, colostrum, etc.) and along the mucosal surfaces of the respiratory, genitourinary, and gastrointestinal tracts. Due to its presence in these fluids and tissues, IgA provides an early defense against invasion by bacteria and viruses.
IgA deficiency is the most common primary immunodeficiency found in humans, affecting about one in every 300 people. This disorder is transmitted as an autosomal dominant trait with incomplete penetrance; thus, everyone who acquires the gene will exhibit some form of the disease, but some will have much milder symptoms than others.
While some individuals affected by IgA deficiency are nearly asymptomatic – and some even remit spontaneously – others develop recurrent respiratory infections (sinusitis, otitis, pneumonia, etc.), diarrhea, or urinary tract infections. Many sufferers are troubled by chronic allergies, and a significant number of patients with IgA deficiency develop autoimmune illnesses. Indeed, in such cases, the autoimmune condition can become more troublesome than the primary immune deficiency and lead to early mortality.
Interestingly, individuals with IgA deficiency can develop antibodies that are directed against IgA (these antibodies would obviously come from other classes, namely IgG, IgM, or IgE). This typically occurs when IgA-deficient persons receive blood products or immune globulins that contain small amounts of IgA; since the IgA is a novel antigen (from the IgA-deficient patient’s point of view), the normal immune response is triggered, and anti-IgA antibodies are formed to reject the “foreign” invader. When the individual is exposed to even minute amounts of IgA in the future, a life-threatening anaphylactic reaction can ensue.
Therefore, if a person with IgA deficiency requires a blood transfusion, he or she should only receive washed red blood cells or frozen blood that has had all extraneous antibodies removed. Additionally, intravenous immunoglobulins should never be administered to people with IgA deficiency. These individuals should wear identification bracelets that alert medical personnel to their condition to prevent the inadvertent administration of IgA-containing blood products.
IgA-deficient individuals who develop autoimmune disorders (lupus, celiac disease, autoimmune hepatitis, Crohn’s disease, ulcerative colitis, etc.) are treated accordingly. Antibiotics and infection control precautions (frequent hand washing, avoidance of crowds, immunizations, prudent travel habits, etc.) are the keystones of treatment for those who are troubled by recurrent infections.