Patterns of infiltration of lymphocytes into the testis under normal and pathological conditions in mice

The testis is known as an immunologically privileged organ. In particular, the blood-testis barrier formed by Sertoli cells protects auto-immunogenic spermatids from attack by the self-immune system. We review here the micro-status of testicular tissues in mice from the viewpoint of induction of inflammatory cell responses. Many studies have demonstrated that the testis is the most resistant to various forms of non-autoimmune inflammation among the male reproductive organs. However, it was found that testicular inflammation of autoimmune origin is inducible by immunization with testis antigens even without an adjuvant in mice. In particular, the tubuli recti (TR) comprises specific region, where lymphocytes are attracted. Many antigen-presenting macrophages preferentially accumulate around the TR under normal conditions. This characteristic accumulation of macrophages is an acquired phenomenon that is completed when spermatids start to differentiate in the seminiferous tubules (S). In addition, intra-tubular lymphocytes that are very close to both germ cells and their remnants could be occasionally found in the TR, rete testis (R), epididymis (E), but not in the S, in normal mice. Although the physiological function of these penetrating lymphocytes remains unknown, we suppose that this micro-status provides a chance for evocation of autoimmune inflammation of the TR, R and E in some pathological conditions.