Antibodies, also called immunoglobulins, are large Y-shaped proteins which function to identify and help remove foreign antigens or targets such as viruses and bacteria. Every different antibody recognizes a specific foreign antigen. This is because the two tips of its “Y” are specific to each antigen, allowing different antibodies to bind to different foreign antigens.
Antibodies are produced by the immune system in response to the presence of an antigen. Antigens are large molecules, usually proteins, on the surface of cells, viruses, fungi, bacteria, and some non-living substances such as toxins, chemicals, and foreign particles. Any substance capable of triggering an immune response is called an antigen.