Complete primary structure of human histocompatibility antigen hla-b7: Evolutionary and functional implications

This chapter focuses on the complete primary structure of human histocompatibility antigen— HLA-B7. The histocompatibility antigens and immunoglobulins are both probably the descendants of some common ancestral gene, which may have originally coded for a cell-bound defense molecule. The development of animals with circulatory systems and duplication of that gene resulted later in an evolution in the secretion of the product of some of these genes into the circulation—i.e., the immunoglobulins. The product of the other genes remained membrane bound and probably went on to evolve to become the histocompatibility antigens. The histocompatibility antigens also serve a defense function for the organism. In this case, the cell-bound defense mechanism may serve to protect the organism from invasion by closely related cells, perhaps serving in primitive organisms to maintain colonial identity on the sea floor. At a different level, the organization of information within a genome can be approached via the cloning of major histocompatibility complex genes by recombinant DNA techniques.