H-Y antigens as Y chromosome-encoded gene products and serologically detectable male antigens (SDM) as testis-or spermatogenesis-linked autosomal gene products

Male-specific transplantation antigen H-Y was proposed to be the testis-det ermining factor (TDF) in 1975, while SRY was found to be the TDF gene in 19 90. What then of H-Y antigen? H-Y antigen was categorized into two entities , vim, T-cell mediated H-Y antigens (H-Y) and serologically detectable male antigens (SDM), Several HY genes such as Smcy, Uty and Dty have been ident ified and these are all Y-linked. H-Y is male-specific and clinically impor tant in cell, tissue, or organ transplantations. Male-enhanced antigen I (M eal) was isolated from an expression library using polyclonal anti-H-Y anti body. We cloned and characterized mouse and bovine Mea1/MEA1, the gene prod uct of which was mainly localized in elongated spermatids, Mea2 was identif ied using monoclonal anti-H-Y antibody. MEA2 protein is localized in the Go lgi apparatus of spermatocytes and spermatids. Colocalization of MEA2 prote in with gamma -adaptin in clathrin-coated vesicles was demonstrated. Disrup tion of Mea2 resulted in spermatogenic failure. These findings suggest that Mea2 is involved in transportation of materials needed for acrosome compon ents in spermatogenesis, Its human homologue is Golgin-160 which was detect ed in an SLE autoimmune disease patient. Mullerian inhibiting substance (MI S) was reported to have SDM activity. Taken together, SDM is a collective n ame for protein antigens associated with testis activity (MIS) or spermatog enesis (MEA1, MEA2) and may be antigenic when expressed in females. From th e viewpoint of autoimmune diseases, the identification and characterization of SDMs will be clinically important.