Structure of immunoglobulins
- Francisco A Bonilla, MD, PhD
Francisco A Bonilla, MD, PhD
- Section Editor — Immunology and Immunodeficiency
- Associate Professor of Pediatrics
- Harvard Medical School
Immunoglobulin molecules are multifunctional tools used by cells to mediate interactions of antigen molecules with a variety of cellular and humoral effector mechanisms. The effector mechanisms include activation of the following systems: signal transduction machinery in the B cell cytoplasm (in the case of surface immunoglobulin receptors), receptors for the constant region of immunoglobulin G (IgG), and the complement system. They also play a role in the afferent limb of the immune system both through antigen presentation and by interacting with regulatory receptors on immune cells.
The basic aspects of immunoglobulin structure will be reviewed here. A discussion of their function, the derivation of monoclonal antibodies, and the various laboratory and clinical applications of immunoglobulin reagents is presented separately. (See "Function and clinical applications of immunoglobulins".)
STRUCTURE OF IMMUNOGLOBULIN PROTEINS
Four-chain unit — The immunoglobulin molecule contains four separate polypeptides (figure 1):
●Two identical light (L) chains of molecular weight (MW) 23 kilodaltons (kd)
●Two identical heavy (H) chains of MW around 55 kd
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