Antibody

Molecular model from X-ray diffraction data (PDB ID: 1igt) of a single antibody. Antibodies (immunoglobulins) are proteins which recognise and neutralise foreign molecules (antigens) in the body, for example some bacteria and viruses. They form part of the immune system that protects us from infection. Antibodies have a characteristic Y-shaped structure which is composed of 2 heavy chains (orange) and 2 light chains (yellow). They also have 2 antigen binding regions (Fab) and a Fc region. Width of image is approximately 16 nm.