Antibodies, also known as immunoglobulins, are glycoproteins produced by B cells that bind to specific antigens. There are five classes of immunoglobulins - IgG, IgM, IgD, IgA, and IgE - which differ in their heavy chains. Immunoglobulins have two primary functions: antigen binding and effector functions like complement fixation and binding to immune cells. Their structure consists of two light chains and two heavy chains that form a Y-shape, with constant and variable regions that determine the class and allow binding to different antigens.

1. Antibody