Relationships among differentiated T-cell subpopulations. V. T-cell dependent mechanism of xenograft rejection and its radioresistant nature.

Rat tumours grew progressively in nu/nu mice but not in nu/+ mice, normal AKR mice or sublethally irradiated AKR mice after subcutaneous inoculation. Suppression of tumour growth appeared to depend on radioresistant cytotoxic T cells which were detected in in vivo neutralization tests (Winn's test) with spleen cells of mice immunized with rat lymphocytes or tumour cells 5 days previously. Radioresistant cytotoxic activity was detected by 51Cr-release test in glass-non-adherent peritoneal exudate cells 5 days after intraperitoneal immunization with rat lymphocytes. These results suggested that immune lymphocytes might differentiate to mature cytotoxic cells at the site of direct graft rejection.