RESPONSE TO LEYDIG-CELL APOPTOSIS IN THE ABSENCE OF TESTICULAR MACROPHAGES

Removal of apoptotic cells from the tissues appears to be a major func tion of resident tissue macrophages. In order to investigate further t he role of testicular macrophages after massive Leydig cell death, adu lt rats were injected intra-testicularly with liposome-entrapped dichl oromethylene diphosphonate (Cl2MDP-lp, right testis) to deplete testic ular macrophages, and with NaCl (left testis) as control. Ten days lat er, the animals were injected intraperitoneally with ethylene dimethan e sulphonate (EDS) to induce Leydig cell apoptosis. In macrophage-cont aining testes there was a 2-fold increase in the number of macrophages on days 1-3 after EDS treatment and Leydig cells were completely elim inated from the interstitium by the second day after treatment. The ma in differences in the response to Leydig cell death in macrophage-depl eted testes were: (1) an early rise in the concentration of small mono nuclear, lymphocyte-like cells, (2) a greater influx of circulating mo nocytes, (3) the existence of variable inflammatory infiltrates on day s 3-4, and (4) the disappearance of infiltrating monocytes by day 10. These results suggest that resident macrophages prevent the inflammato ry reaction elicited by massive Leydig cell death.