Intratesticular grafts: the testis as an exceptional immunologically privileged site.

The testis is an immunologically privileged site despite a normal lymphatic drainage, whereas the anterior chamber of the eye is a privileged site because it lacks normal lymphatics. Parathyroid grafts were transplanted between several strains of inbred rats (Buffalo leads to Lewis and Lewis X Brown Norway F1 leads to Lewis). Allografts were placed in the testis, thigh muscle, prostate, lymph nodes, anterior chamber of the eye and adrenal gland. The survival of intratesticular allografts also was tested in animals whose pituitary gonadotropins were suppressed by testosterone and estradiol implants. The effects of steroid implants were documented by measuring testosterone and progesterone concentrations in the serum and whole testis homogenates of these animals. Allograft survival was judged by fasting plasma calcium concentrations. The data show that 1) the adrenal is included among naturally occurring immunologically privileged sites, 2) the prolonged survival of intratesticular allografts may be related to the local production of steroid hormones, although allograft survival is not critically dependent on pituitary gonadotropins and 3) temperature differences and a high zinc concentration within the testis are not important to allograft survival.