H-Y antigens, testis differentiation, and spermatogenesis.

H-Y antigen defined by graft rejection and by cytotoxic T cell action ('transplantation H-Y') appears to be different from H-Y antigen that is characterized by antibodies ('serological H-Y'). Gene(s) for the transplantation H-Y were assigned to the long arm or to the centromeric region of the human Y chromosome. A regulatory gene for serological H-Y seems to be located in a distal region of the Y short arm. Various investigations suggest that serological H-Y has a molecular weight of approximately 18,000. While serological H-Y might be involved in the differentiation of the heterogametic gonad of vertebrates, transplantation H-Y may be required for normal spermatogenesis to occur in mammals.