Gastroenterology MCQ Answer 33

Answer: b

Gut-associated lymphoid tissue (GALT) represent a major division of the immune system and is made up of aggregated (Peyer’s patches, lymphoid follicles, mesenteric lymph nodes) and nonaggregated cellular components. The lamina propria of the small intestine contains a wide array of nonaggregated lymphoid tissue including B cells, T cells, macrophages, eosinophils, and mast cells. Some 80% to 99% of B cells are active producers of immunoglobulin A (IgA). In comparison, only 2% to 5% of B cells found in other lymphoid tissues of the body secrete IgA. IgA is the major immunoglobulin of the intestinal immune system. The functional characteristics of IgA are unlike those of other antibodies. Unlike IgG or IgM, secretory IgA does not induce Fc-mediated inflammatory reactions. Antigen-IgA complexes do not activate the classic or alternate complement systems, nor does IgA promote the phagocytosis of bacteria by opsonization. Most of the protective effect of IgA derives from its ability to bind the threatening antigen efficiently, while resisting enzymatic degradation by gut enzymes.

Category: Gastroenterology MCQs