Antibodies

Antibodies or immunoglobulins (Igs) are soluble proteins secreted by activated B cells or by their plasma-cell offspring in response to an antigen and are capable of binding specifically with that antigen.

An antibody is composed of four polypeptide chains (two heavy and light) that form a T- or Y- shaped molecule.

There are five classes of antibodies:

• IgA
• IgG
• IgM
• IgD
• IgE

Antibody functions include complement, fixation, neutralization, precipitation, and agglutination.