An isotype refers to any related proteins from a particular gene family. In immunology, the "immunoglobulin isotype" refers to the phenotypic variations in the constant regions of the heavy and light chains. In humans, there are five heavy chain isotypes and two light chain isotypes:
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 (γ1), etc. are isotypes of heavy chains. All isotypes can be readily found in normal sera.
- Immunoglobulin Isotypes at the US National Library of Medicine Medical Subject Headings (MeSH)
- Overview at University of South Carolina School of Medicine
- Overview at Southern Illinois University Carbondale