INFLUENCE OF HISTOCOMPATIBILITY AND TRANSPLANT SITE ON PARATHYROID ALLOGRAFT SURVIVAL

Despite the finding that even weakly histoincompatible parathyroids were usually rejected promptly in transplant sites of rich lymphatic vascularity, parathyroid allografts seemed to enjoy a significant advantage in longevity over skin and hearts transplanted across the same barriers. Thus, parathyroid tissue is apparently immunologically privileged. The influence of histocompatibility and transplant site on parathyroid allograft survival was studied in inbred rats. Ag-B compatible grafts survived longer than Ag-B incompatible ones in all transplant sites. When care was taken to place parathyroid allografts in transplant sites having rich lymphatic drainage, prolongation of survival was minimal, and rejection took place within 23 days in almost every instance. In other transplant sites sharing the characteristic of absent or abnormal lymphatic drainage (skin islands, muscle and possibly testicle), prolonged parathyroid survival was seen in a high percentage of animals. Previous reports of inconsistencies in parathyroid allograft survival probably can be explained on the basis of variation in the lymphatic revascularization of the individual glands in different transplant sites.