Isotype (immunology)

Some antibodies form complexes that bind to multiple antigen molecules.

An isotype usually refers to any related proteins/genes from a particular gene family. In immunology, the "immunoglobulin isotype" refers to the genetic variations or differences in the constant regions of the heavy and light chains. In humans, there are nine heavy chain isotypes and two light chain isotypes:

• heavy chain
  • α - IgA 1, 2
  • δ - IgD
  • γ - IgG 1, 2, 3, 4
  • ε - IgE
  • μ - IgM
• light chain
  • κ
  • λ

Immunoglobulin class switching can be used to change the class of the heavy chain, but not of the light chain.

Isotypes are distinct forms of light or heavy chains which are present in all members of a species, encoded at distinct genetic loci. Kappa and lambda are isotypes of light chains. Delta (δ), gamma:1 (δ1), etc are isotypes of heavy chains. All isotypes can be readily found in all normal sera.

See Also

• idiotype

External links

• MeSH Immunoglobulin+Isotypes
• Isotype at eMedicine Dictionary
• Overview at University of South Carolina School of Medicine
• Overview at Southern Illinois University Carbondale