The Influence of Extracorporeal Irradiation of the Blood and Lymph on Skin Homograft Rejection

Small lymphocytes are generally considered immunologically competent cells (1-7). There is fairly good evidence that the homograft rejection is mediated primarily through viable cells rather than through soluble antibodies (8-10). It is further believed that the homograft rejection is dependent on immunologically competent cells circulating in the blood stream and that the antibodies involved in the reaction are cell-bound (10-15). As a result of the clear-cut involvement of lymphocytes in the homograft rejection process (16-19), there have been numerous attempts to ablate or suppress lymphoid tissue in order to alter the homograft rejection. Surgical removal of lymphoid tissue (16, 20), RES blockade by Trypan Blue (14), administration of cortisone (21), and high doses of X-rays (22) have been utilized. McGregor and Gowans (23) have significantly prolonged the rejection of skin homografts by depletion of lymphocytes from rats with thoracic duct drainage. Gray et al. (24) have suppressed lymphocytes by antilymphocyte serum to prolong homograft survival. Woodruff et al. (25) combined thoracic duct drainage with antilymphocyte serum to influence the homograft rejection process. In our laboratory, extracorporeal irradiation (ECI) of the blood has been used alone or in combination with thoracic duct drainage to produce a lymphocytopenia and to study the production and migration of lymphocytes (26, 27). The depletion of lymphoreticular organs of lymphocytes by ECI has been described by Cottier et al. (28). In this paper the influence of ECI of the blood and lymph on skin homograft rejection in calves will be reported.