Macrophage populations in L-cysteine-induced rat sperm granulomas.

Histopathologically, sperm granulomas consist of a central mass of degenerating spermatozoa surrounded by many epithelioid macrophages and lymphocytes. Using monoclonal antibodies (ED1, ED2, and OX6), the authors investigated immunohistochemically the participation of different macrophage populations in epididymal sperm granulomas induced in pubertal rats by repeated injection of L-cysteine. Monocyte-like and epithelioid macrophages expressed the ED1 antigen found on activated lysosomal membranes in rat blood monocytes and exudate macrophages, but did not express the ED2 antigen found on the membrane antigens of rat resident macrophages. Cells expressing MHC class II antigens (as detected by the OX6 antibody) were present in the granulomas in moderate numbers, particularly in the early stages. Ultrastructurally, fragmented spermatozoa were observed in the cytoplasm of epithelioid macrophages. These findings suggest that macrophages appearing in rat sperm granulomas originate mainly from blood monocytes, and that they have a high phagocytic activity and a potential for antigen presentation.