Fetal and postnatal testis shows immunoprivilege as donor tissue.

We evaluated the immunogenicity of the testis by transplanting adult, postnatal, and fetal rat testicular tissue into outbred adult female and male rats for 10 days. Testis grafts were evaluated morphometrically and histologically, and selectively compared to renal grafts previously reported in part. Testis grafts from days 15 to 21 of gestation, and from three, nine, 12 and 15 days after birth showed an overall increase in growth, with maintenance of architecture and minimal lymphocytic infiltrate. In contrast, only fetal renal tissue from days 15 to 17 demonstrated an increase in growth with maintenance of architecture and minimal lymphocytic infiltrate; grafts from later in gestation grew only slightly and showed progressive deterioration in architecture with an increasing lymphocytic infiltrate. Fifteen day fetal testis grafts were also implanted for longer intervals up to 45 days. The fetal testis grafts implanted for 20 and 30 days showed an increase in size with maintenance of architecture and minimal lymphocytic infiltrate. The observed fetal and postnatal testis growth in the non-immunosuppressed adult host makes compelling further studies directed at determining those factors contributing to the decreased immunogenicity of this organ.