AP BIOLOGY

Detailed explanation-1: -IgA is the most abundant antibody isotype in mucosal secretions and owes its success in frontline immunity to its ability to undergo transcytosis across epithelial cells.

Detailed explanation-2: -The IgA dimeric form is the most prevalent and is also called secretory IgA (sIgA). sIgA is the main immunoglobulin found in mucous secretions, including tears, saliva, sweat, colostrum and secretions from the genitourinary tract, gastrointestinal tract, prostate and respiratory epithelium.

Detailed explanation-3: -The mucosal immune system contains more than 80% of all Ig-producing cells in the body, and the major product of these cells in normal individuals is IgA.

Detailed explanation-4: -IgM and IgA are actively secreted to mucous membranes by engaging the pIgR and thereby forming SIgM and SIgA 4, although IgG is also found to be present at mucosa, especially in the lungs, due to FcRn-mediated transport 5. The amounts of SIgA are normally higher than those of SIgM.

Detailed explanation-5: -The immunoglobulin A (IgA) is the predominant antibody isotype in the mucosal immune system, which widely exists in the gastrointestinal tract, respiratory tract, vaginal tract, tears, saliva, and colostrum. Normally, serum IgA shows a monomeric structure, while the mucosal IgA shows polymeric.