Immunoglobulin

Immunoglobulins are proteins produced by, and active in, the immune system. They are produced by B lymphocytes, from the effects of both genes and antigens. Immunoglobulins are responsible for humoral immunity, or immune reactions controlled by antibody molecules in the body.

Structurally, they have two heavy and two light chains, and, depending on the specific immunoglobin, additional polypeptide chains. There can stay as single proteins, or polymerize into more complex structures.

The transmembrane forms become antigen receptors on the B-cells. When activated, the B-cells secrete immunoglobins as antibodies.

They divide into major classes based on the amino acid sequencing of their heavy chains. The classic way to separate the major classes is electrophoresis, although much more complex methods are used to recognize specific antibodies.