Immunoglobulin A antigen reactions. Immunoglobulin A (Chapter 22)is the principal immunoglobulin in such human secretions as saliva, bile, and gastric juice. Class-specific anti-IgA occurs in patients who lack IgA; these persons may be clinically normal or may have such disorders as malabsorption syndrome, autoimmune disease, or recurrent sinus or pulmonary infection. Interestingly, only 40% develop […]