Which subclass of IgA is primarily secreted in mucosal areas?

The subclass of IgA that is primarily secreted in mucosal areas is IgA2. Secretory IgA, which is found in mucus, saliva, tears, and breast milk, plays a crucial role in the immune defense of mucosal surfaces, protecting against pathogens entering through these routes. IgA1 and IgA2 both exist in the human immune system, but IgA2 is more commonly produced in mucosal areas due to its unique structure, which is better suited for persistent exposure to pathogens and environmental factors found in these regions.

IgA1, while present in the serum and certain secretions, is more predominant in the blood and is more susceptible to proteolytic enzymes, which makes IgA2 more advantageous for mucosal immunity. On the other hand, IgD and IgE are immunoglobulins with different functions and roles in the immune system. IgD is primarily involved in B cell activation and development, whereas IgE is associated with allergic responses and protection against parasitic infections.