Which antibody is found in body secretions such as tears and saliva and can exist as a secretory dimer?

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Multiple Choice

Which antibody is found in body secretions such as tears and saliva and can exist as a secretory dimer?

Secretory IgA is specialized for protecting mucosal surfaces. In tears and saliva it is present as a dimer joined by a J chain, and epithelial cells add a secretory component that shields it from proteolysis as it passes through harsh secretions. This secretory dimer form lets IgA neutralize microbes and toxins right at the entry points, preventing adhesion and invasion before they reach the rest of the body. Other isotypes are primarily found in blood or tissues rather than secretions: IgG is mainly in serum and provides systemic protection, IgM is a larger pentamer that appears early in the response, and IgE is involved in allergic responses and anti-parasite defenses. So, the antibody found in body secretions and able to exist as a secretory dimer is IgA.

Secretory IgA is specialized for protecting mucosal surfaces. In tears and saliva it is present as a dimer joined by a J chain, and epithelial cells add a secretory component that shields it from proteolysis as it passes through harsh secretions. This secretory dimer form lets IgA neutralize microbes and toxins right at the entry points, preventing adhesion and invasion before they reach the rest of the body. Other isotypes are primarily found in blood or tissues rather than secretions: IgG is mainly in serum and provides systemic protection, IgM is a larger pentamer that appears early in the response, and IgE is involved in allergic responses and anti-parasite defenses. So, the antibody found in body secretions and able to exist as a secretory dimer is IgA.

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