Reproductive immunotoxicology with special reference to male reproductive organ

Spermatozoa do not appear in the seminiferous epithelium until puberty, when immune tolerance already has been established. Therefore, they contain various autoimmunogenic materials which are recognized as foreign by the self-immune system. However, the testis is known as immunologically privileged organs. In particular, the blood–testis barrier (BTB) formed by Sertoli cells protect autoimmunogeneic spermatozoa from attack by the self-immune system. The immune privileged circumstances in the testis has been demonstrated by many studies to involve a local transplantation system. The testicular interstitium in mice is resistant to vasculitis, lymphangitis, spermatic granuloma and polymorphonuclear cell infiltration. Therefore, the testicular tissue outside BTB is also protected from inflammatory cell infiltration, although many resident macrophages are normally present in the testis. In sharp contrast, subcutaneous injection of viable syngeneic testicular germ cells (TGC) alone induces experimental autoimmune orchitis (EAO) in mice. In the testes of TGC-immunized animals, severe lymphocytic infiltration with aspermatogenesis was seen in spite of no use of adjuvants. Moreover, cadmium chloride (CdCl₂) and di-(2-ethylhexyl) phthalate (DEHP) as environmental toxicants is known to affects the immune system by acting as an adjuvant, recently, it also became evident that exposure to a low-dose of them affect the testicular immune-system. In this meeting, we show the immune privileged status of these organs from the viewpoint of induction of immune-responses induced by EAO and environmental toxicants.