Immunohistochemical detection of testicular macrophages during the period of postnatal maturation in the mouse

In the present study, the distribution of F4/80, a highly specific antigen of murine macrophages, was studied in the testes of maturing ICR mice to investigate postnatal development of testicular macrophages. The antigen was immunohistochemically identified at the light microscopic level on days 0, 7, 14, 21, 28 and 42 and at 8 weeks after birth. Only a few macrophages were present between developing seminiferous tubules on day 0, but by day 7, the cell density of macrophages in the interstitium was significantly increased. Although the cell processes of the macrophages were very short on days 0 and 7, it was found that their cell processes were extended on days 14 and 21. On day 28, it was observed that the cell density of macrophages increased further and their cell processes became longer, resulting in the formation of a network between adjacent macrophages. Thereafter, the interstitial spaces were found to be narrower due to the increasing diameter of developing seminiferous tubules, although similar physical contact between the testicular macrophages to that seen on day 28 was evident. Moreover, the cell density of macrophages at 8 weeks of age did not differ significantly compared with that on day 28. These results demonstrate that testicular macrophages develop rapidly for the first 4 weeks in the mouse testis.