Where is IgA predominantly found?

Where is IgA predominantly found?

• A. Blood plasma
• B. Brain tissue
• C. Mucosal areas such as the gut, respiratory and urogenital tracts, and secretions like saliva, tears, and breast milk
• D. Lymph nodes only

Answer: (C)

IgA is the antibody most characteristic of mucosal immunity, found predominantly at mucosal surfaces and in secretions. It is produced by plasma cells in mucosa-associated lymphoid tissue and appears mainly as secretory IgA, a dimer bound to a secretory component that protects it from digestion in harsh mucosal environments. This form is transported across epithelial cells into the lumen of the gut, airways, and urogenital tract, and is present in saliva, tears, and breast milk, where it helps neutralize pathogens at the points of entry. In blood, IgA exists but is not the major circulating antibody—other immunoglobulins, especially IgG, predominate there. Brain tissue is not a primary site for IgA, and lymph nodes, while important immune hubs, do not house IgA as its main functional form. So the best description is that IgA is found mainly in mucosal areas and their secretions, such as the gut, respiratory and urogenital tracts, and in saliva, tears, and breast milk.

IgA is the antibody most characteristic of mucosal immunity, found predominantly at mucosal surfaces and in secretions. It is produced by plasma cells in mucosa-associated lymphoid tissue and appears mainly as secretory IgA, a dimer bound to a secretory component that protects it from digestion in harsh mucosal environments. This form is transported across epithelial cells into the lumen of the gut, airways, and urogenital tract, and is present in saliva, tears, and breast milk, where it helps neutralize pathogens at the points of entry. In blood, IgA exists but is not the major circulating antibody—other immunoglobulins, especially IgG, predominate there. Brain tissue is not a primary site for IgA, and lymph nodes, while important immune hubs, do not house IgA as its main functional form. So the best description is that IgA is found mainly in mucosal areas and their secretions, such as the gut, respiratory and urogenital tracts, and in saliva, tears, and breast milk.