Understanding the testes immunological sanctuary: an in vitro human Sertoli cell study

Abstract

OBJECTIVE: The immunological “sanctuary” of the testis is theorized to have 2 components: a passive, physical “blood-testis” barrier formed by inter-Sertoli tight junctions and a localized active immunosuppressive “field effect”. To better understand active immunosuppression of human testis, we analyzed the presence of an immunoregulatory lectin, Galectin-1, in testis cryosections and in a primary human Sertoli cell model. DESIGN: Controlled immunohistochemical studies in human testis and in an in vitro human Sertoli cell model. Jurkat E-6 T cell proliferation assays in the model. MATERIALS AND METHODS: Human Sertoli cells were isolated from fresh cadaveric tissue. Intact tissue and derived primary Sertoli cell were analyzed by immunostaining and by FACS. Sertoli cells were cultured as monolayers, or as polarized monolayers or spheroids in semipermeable transwell chambers by proprietary methods. Immunostaining was performed with GATA4 (positive Sertoli marker), and Galectin-1. The effect of Sertoli cell conditioned media on Jurkat E-6 T cell proliferation was analyzed by metabolic dyes. The effect of direct Sertoli cell contact on CFSE-stained Jurkat T cell proliferation was assessed by FACS. RESULTS: Galectin-1 and GATA4 localized to Sertoli cells in the testis cryosections, and >90% of Sertoli cell-enriched cultures expressed GATA4. Immunoblots confirmed Galectin-1 expression and secretion by Sertoli cells. Conditioned media from Sertoli monolayers, and direct Sertoli cell contact in transwells reduced Jurkat proliferation. CONCLUSIONS: The immunosuppressive Galectin-1 localizes to human Sertoli cells in testes and in vitro. T cell proliferation was suppressed by conditioned media, and by direct Sertoli cell contact. The results suggest that active immunosuppression may exist in the human seminiferous tubule and that secreted Galectin-1 could be important for this field effect.