Which immunoglobulin is primarily involved in mucosal immunity?

The immunoglobulin primarily involved in mucosal immunity is IgA. This is because IgA plays a crucial role in protecting mucosal surfaces, such as those of the gastrointestinal, respiratory, and urogenital tracts. It is secreted in high concentrations in mucosal secretions like saliva, tears, and breast milk, where it acts by neutralizing pathogens and preventing their adherence to epithelial cells.

IgA exists in two main forms: monomeric IgA found in serum and dimeric IgA, which is predominant in secretions. The dimeric form helps provide a robust defense against infections at mucosal surfaces by forming larger complexes that are effective in trapping and eliminating pathogens.

Other immunoglobulins, such as IgG, play important roles in systemic immunity and resolving infections in tissues rather than specifically targeting mucosal areas. IgM is primarily involved in the early stages of immune response, particularly in identifying and neutralizing pathogens in the circulatory system. IgE is mainly associated with allergic reactions and responses to parasitic infections, rather than with mucosal immunity. Thus, IgA is the key player in the defense mechanism at mucosal sites.