Immunologic privilege and the testis

The testis has long been regarded as a site particularly hospitable to grafts of foreign tissue, evidenced primarily from studies with tumors in oubred animals, and so joins that group of well known privileged sites that includes the anterior chamber of the eye, the brain, and the hamster's cheek pouch. Although the privileged status of these sites has usually been attributed to their lack of lymphatic drainage, we have recently shown that the rat's testis has a very effective lymphatic drainage, involving primarily the iliac and renal lymph nodes. Others have shown that the testicular interstitial connective tissue is laced with a complex, fine lymphatic network. We have therefore undertaken an investigation of the extent and nature of immunologic privilege in the testis, using inbred animals and parathyroid gland allografts so that functional activity within the testicular milieu could be monitored.