Immunomorphological aspects of the tubuli recti and the surrounding interstitium in normal mice

The tubuli recti (TR) are immunologically special, because the lymphocytes preferably accumulate around them during the course of T-cell dependent testicular autoimmunity in mice. This finding implies that the testicular interstitium around the TR is where autoreactive lymphocytes can gain access to autoimmunogenic germ cell antigens. In the present study, the histoarchitecture of the TR was minutely examined in normal mice. Three-dimensional analysis showed that 14-16 TR appeared to be connected to the rete testis (RT). Electron microscopical analysis revealed that the epithelial cells in the TR formed protruding cytoplasmic strings, with active endocytosis of degenerated spermatozoa, and exhibited three different morphological characteristics. Furthermore, a few macrophages were found to have penetrated into the TR. Immunohistochemical image analysis revealed that more macrophages specifically accumulated around the TR than the RT or seminiferous tubules. These findings indicate that macrophages preferentially accumulate around the TR, where contact between germ cell antigens and macrophages may occur under normal and pathological conditions.