Immunoglobulin A (IgA) is a type of antibody that plays a crucial role in the immune system. It is primarily found in mucosal areas, such as the gut, respiratory tract, and saliva, helping to protect these surfaces from infections. IgA is essential for defending against pathogens that enter the body through mucosal membranes. There are two main forms of IgA: serum IgA, which circulates in the blood, and secretory IgA, which is present in bodily secretions like tears and breast milk. Secretory IgA is particularly important for infants, as it provides passive immunity through breastfeeding, helping to shield them from infections during early development.