Acrosomal Component of Rat Round Spermatids Recognized by a Novel Monoclonal Antibody

OBJECTIVE: To characterize immunocytochemically the antigen recognized which appears at specific stages of germ cell development and acrosomal biogenesis by the novel monoclonal antibody (Mab 3C2). METHODS: The novel monoclonal antibody (Mab 3C2) raised against testicular Sertoli and germ cells. RESULTS: The immunoreactivity of this Mab in testicular sections from immature 20-day-old rats was confined to the pachytene spermatocytes. In adult testis the Mab 3C2, besides meiotic cells, recognized also acrosomal component of round spermatids. The immune reaction was observed in Golgi and cap phases of acrosomal development until the stage VIII of the cycle of the seminiferous epithelium. Immunostaining was absent in acrosome of elongating and mature spermatids and indicated that some modifications in acrosomal protein may exist in subsequent stages of acrosomal development. CONCLUSIONS: Novel Mab 3C2 shares a common antigen in pachytene spermatocytes and round spermatids. Therefore, it may be a marker of meiotic and postmeiotic germ cells.