Modification of Skin Allograft Immunity by Extracorporeal Irradiation of Lymph

Thoracic duct lymphocytes of calves were continuously destroyed by extracorporeal irradiation of the lymph (ECIL) for up to 68 days. Skin grafts which were placed within the drainage bed of the thoracic duct (posterior grafts) were compared to grafts from a second donor which were not drained exclusively by the thoracic duct (anterior grafts). Pregraft ECIL for 10–22 days produced lymphopenia and prolonged survival of anterior and posterior grafts for 8–10 days. When ECIL was continued after grafting, anterior grafts were rejected as before, but posterior grafts remained intact until ECIL was discontinued. Postgraft ECIL delayed and markedly suppressed the cytotoxic antibody activity in the serum although small amounts could be detected while grafts were intact. Following the termination of ECIL, the cytotoxic activity increased, however, at the time of rejection it was still well below that found in untreated calves.