Immunohistochemical localization of yolk sac antigen 1 on rat spermatogenic cells.

The reactivity of monoclonal antibody (6D1, mAb) directed against yolk sac antigen 1 was verified on testes of young and adult rats. The antigen defined by 6D1 mAb was detected on the earliest appearing pachytene spermatocytes in the testis of 18-day-old rats. In the testis of the adult rat, the mAb reacted with pachytene spermatocytes, spermatids and spermatozoa. Less differentiated cells of spermatogenesis, for example spermatogonia and early spermatocytes, showed no reaction with the 6D1. Only after breaking down the blood-testis barrier, could the mAb injected intravenously reach the spermatogenic cells of the adluminar compartment in the seminiferous tubules.