Biochemistry, Immunoglobulin A

Excerpt

Immunoglobulin A (IgA), one of the five primary immunoglobulins, plays a pivotal role in mucosal homeostasis in the gastrointestinal, respiratory, and genitourinary tracts, functioning as the dominant antibody of immunity in this role. It is the second most abundant immunoglobulin type found in the body and, consequently, has a crucial role in protection against antigens. IgA production is greater than all other immunoglobulin subtypes, necessary for the many roles it plays systemically.

IgA gets produced by class switching of Ig, which is regulated by various processes. The binding of CD40-CD40L and secretion of other cytokines IL-4, IL-5, IL-6, IL-10, and IL-21 promote maturation of Th2 cells, which promote class switching to different Ig subtypes. Retinoic acid, a metabolite of vitamin A, synergistically acts with IL-5 and IL-6 to induce IgA secretion as well.