A group of naturally occurring proteins that act as ANTIBODIES. They are structurally related, their differences determining their biological behaviour. Humans have five types of immunoglobulin with different protective functions: IgA, IgD, IgE, IgG and IgM. In the laboratory these are separated and identified by a chemical process, electrophoresis.

Certain immunoglobulins can be used in the active or passive immunity of people against infectious diseases such as RABIES and viral HEPATITIS (IMMUNITY and GAMMA-GLOBULIN). They are also used in treating certain immunological conditions such as KAWASAKI DISEASE.