Immunohistochemical Studies and Functional Implications of CTLA‐2 Alpha in Mouse Testis, Epididymis, Seminal Vesicle and Prostate Glands

CTLA-2 alpha, a cysteine protease inhibitor, shares structural homology with pro-region of cathepsin L, to which it exhibits specific and potent inhibitory activity. Sertoli cells secrete cathepsin L which participates in spermatozoa production and maturation in testis and epididymis. Sertoli cells also regulate activity of regulatory T cells, helper T cells and cytotoxic T cells to prevent autoimmune attack on developing spermatogenic cells. Mast cells and activated T cells were first cells identified to express CTLA-2 alpha. CTLA-2 alpha mRNA is expressed by undifferentiated spermatogonia but its protein has never been demonstrated in testis, not even in other male reproductive organs. This study therefore aimed at investigating by immunohistochemistry CTLA-2 alpha localization in testis, rete testis, efferent duct, epididymis, deferens duct, seminal vesicles and prostate. Results showed localization of CTLA-2 alpha in Leydig cells, Sertoli cells, spermatogonia, spermatocytes, spermatids and spermatozoa, as well as in epithelial cells lining rete testis, efferent ducts, epididymis including spermatozoa, deferens duct and prostatic urethra. Basal cells and principal cells of initial segment of epididymis showed weak staining. In accessory sex glands, staining was detected in apical portion of cytoplasm of epithelial cells lining seminal vesicles. In prostate, staining was diffusely distributed in cytoplasm of luminal epithelial cells. Extension of prostate cell apical cytoplasm into lumen was frequently encountered in anterior and dorsal prostate, representing apocrine release of secretory products. Localization of CTLA-2 alpha in male reproductive system is suggestive of its potential roles in regulation of spermatogenesis in testicular tissues, maturation of spermatozoa in tubular structures and secretion of proteins and peptides by seminal vesicles and prostate essential for male fertility.