Histopathology of the tubuli recti at the start of experimental autoimmune orchitis in mice.

We previously established an experimental model of autoimmune orchitis (EAO) by means of immunization with testicular germ cells (TGC) alone in mice and confirmed that the disease can be transferred to mice that had received CD4+ but not CD8+ or B lymphocytes obtained from TGC-immunized donor mice. The tubuli recti (TR) are special in that lymphocytes first accumulate around them before spreading to the peripheral seminiferous tubules in EAO. However, the minute changes in the TR remain unknown. Therefore, we investigated the histopathology of the TR before the induction of spermatogenic disturbance. The results revealed that the first infiltrating lymphocytes around the TR were not only of T-cell but also of B-cell lineage. Moreover, it was also shown that some of these infiltrating lymphocytes migrated into the TR, with resultant degeneration of the TR epithelium before damage to the seminiferous epithelium. These findings indicate that TR epithelial cells are the first targets of autoreactive T and B lymphocytes in EAO.