What are the main functions of IgA?

The primary functions of Immunoglobulin A (IgA) are centered around its role in mucosal immunity, which is crucial for protecting body surfaces that are exposed to external pathogens. IgA is primarily found in mucosal areas, such as the gastrointestinal tract, respiratory tract, and urogenital tract, as well as in secretions like saliva, tears, and breast milk. Its presence in these areas helps to prevent pathogens from adhering to and penetrating epithelial cells, thereby providing a first line of defense against infections.

By protecting against invading microorganisms, IgA plays an essential role in neutralizing potential threats at mucosal surfaces before they can cause illness. Additionally, IgA contributes to the prevention of anaphylactic reactions by blocking allergens from binding to their receptors on cells, thus mitigating the severity of allergic responses.

The other options relate to the functions of different immunoglobulins or immune mechanisms. For instance, while some antibodies neutralize toxins and kill microbes, this is more characteristic of IgG and IgM. Similarly, while phagocytosis is enhanced by opsonization (which involves other antibodies such as IgG), IgA's primary function does not involve complement pathways or directly enhancing phagocytosis in the same way. IgA