What are Histocompatibility Molecules?

The specific glycoprotein molecules expressed on the surface of almost all vertebrate cells are referred as “histocompatibility molecules”. Histocompatibility molecules are unique in nature.

Except in identical (Monozygotic) twins, no two individuals show the same type of molecules.

The histocompatibility molecules of one individual act as antigens, when they are introduced into another individual.

Hence they are often referred as histocompatibility antigens or transplantation antigens. With reference to their role in graft rejection histocompatibility molecules are classified in to two types.

One is major histocompatibility molecules (MHC) that have major influence on transplant (graft) and the other type is minor histocompatibility molecules that have negligible impact on graft rejection.