(Proteins produced by B cells that help recognize and bind foreign substances (antigens) to help neutralize and eliminate them. There are five major types:

• IgE (involved in immediate allergic reactions and defense against parasites),
• IgA (important for mucosal immunity at surfaces such as the GI tract, respiratory tract, and secretions like saliva and tears),
• IgG (the most abundant class, important for clearing infection and long-term immunity),
• IgM (early immune response),
• IgD (receptor on B cells).