Leukocyte Populations of the Adult Rat Testis Following Removal of the Leydig Cells by Treatment With Ethane Dimethane Sulfonate and Subcutaneous Testosterone Implants1

The influence of the Leydig cells on the leukocyte population of the testis was investigated. Leydig cells were destroyed by ethane dimethane sulfonate (EDS) treatment in adult male rats, with or without low-dose s.c. testosterone implants to prevent Leydig cell recovery. Leukocytes were counted in perfusion-fixed frozen testis sections, by use of cell-specific monoclonal antibodies (mAbs) with immunoperoxidase detection, or toluidine blue staining. The majority (81%) of testicular leukocytes (OX1+) were immunopositive for the resident macrophage-specific mAb, ED2, and/or the monocyte/macrophage/dendritic cell mAb, ED1. The remaining leukocytes were principally T lymphocytes (R73+). B lymphocytes (OX33+) and metachromatic mast cells were not observed in the normal testis. Treatment with EDS caused a transient increase in ED1+, ED2+, and R73+ cell numbers in the testis, although other evidence of an inflammatory reaction, such as increases in major histocompatibility complex class II antigen, interleukin-2 receptor expression, or capillary permeability, were not observed. At 21 days after EDS treatment, there was a significant decline in macrophage numbers (to approximately 50% of control testis), and T lymphocytes returned to pretreatment levels. After Leydig cell recovery (41 days after treatment), macrophages also returned to pretreatment levels in EDS-treated rats, but remained reduced in EDS-treated animals with testosterone implants. In addition, EDS treatment stimulated a progressive increase in intertubular mast cells, which was significantly inhibited in the testosterone-implanted rats. The data indicate that numbers of testicular macrophages and mast cells, but not of lymphocytes, within the adult rat testis are directly or indirectly regulated by the Leydig cells.