The H-2 Complex and Somatic Cell Genetics

Abstract

For more than half a century, mammalian genetics has been concerned almost exclusively with the mechanisms by which genetic information is transmitted through germ cells; an inquiry into the principles governing the expression of genetic information in somatic cells has only recently begun. The genetics of somatic cells is aimed at understanding such phenomena as differentiation, antibody formation, neoplasia, and cell-virus interaction. The existence of somatic cell genetics is dependent upon the ability to detect variant forms (variants) of somatic cells, that is, rare deviations from the norm, which can then be used as markers in genetic analysis. The markers must fulfill two major criteria: they must be expressed in an easily detectable form in the somatic cells, and they must provide ways of selecting a new variant from a population of normal cells. The antigens controlled by the H-2 complex meet both these criteria: they can be detected in all, or almost all normal and neoplastic tissues using a variety of relatively simple serological tests, and they can be subjected to a strong selection pressure in the form of an immune reaction. It is therefore not surprising that H-2 antigens have frequently been used in somatic cell genetics and have contributed considerably to the development of this field. Only one example of this contribution—the variant formation (both specific and nonspecific) in tumor cells—will be considered here.