Phagocytosis by the murine testicular TM4 Sertoli cell line in culture

Abstract

To investigate phagocytosis, an assay enabling flow cytometric analysis of single cells having internalized fluorescent carboxyl microspheres was employed. Greater than 80% of murine testicular Sertoli line (TM4) cells were found to phagocytose one or more microspheres within six hours and electron microscopy confirmed carboxyl microsphere internalization. This level was equivalent to that of a macrophage-like cell line and much greater than the levels of testicular Leydig (TM3) cells. Reducing extracellular calcium or using a calcium channel blocker profoundly inhibited phagocytosis suggesting that phagocytosis by Sertoli cells requires extracellular Ca++. Although follicular stimulating hormone, luteinizing hormone, and testosterone had no significant effects on Sertoli cell phagocytosis, insulin, epidermal growth factor, and hydrocortisone enhanced activity. In contrast, beta-endorphin and 8-bromoadenosine-cyclic monophosphate had an inhibitory effect. In contrast to augmenting macrophage phagocytosis, 1,25-(OH)2D3, interferon-gamma, prostaglandin E2, and lipopolysaccharides, had no apparent effect on that by Sertoli cells. Additionally, neither C3bi receptors (Mac-1 antigen) nor FcRII could be detected on Sertoli cells. In total, the findings demonstrated that the murine Sertoli line exhibits potent phagocytic function and suggest the regulation of this activity may differ from that in "professional" phagocytic cells.