Immunodeficiency and mucosal immunity

This chapter outlines the information about gastrointestinal conditions. Secretory IgA (S-IgA) binds commensal flora and other intestinal antigens and is considered an important part of the T-cell-independent mucosal immune system. This antibody is produced in great abundance and has a complex synthetic and secretory pathway. IgA deficiency is the most common primary immune deficiency disease of humans. The lack of S-IgA leads to a variety of infections and inflammatory conditions, but for each deficiency disease the manifestations vary. Whatever genetic abnormality may underlie IgA deficiency, it is not always a stable defect, since IgA deficiency can disappear spontaneously, can be induced by viral infections, and can be caused by a number of disparate drugs such as-phenytoin, penicillamine, captopril, and Tegretol. Males with X-linked gammaglobulinemia (XLA) have an excellent T-cell immunity, whereas subjects with common variable immunodeficiency disease (CVID) usually have T-cell defects. Studies in knockout mice indicate an essential role for T cells and cytokine regulation in intestinal mucosal integrity. It is the lack of these regulatory factors that predisposes patients with CVID to inflammatory mucosal diseases.