[Suppression of the cell-mediated immunity in minor histoincompatible rat kidney allograft recipients (author's transl)].

To study the immunological status of recipients of major compatible and minor incompatible kidney allografts, we transplanted FiS and FLF1 kidneys into LEW rats. Most of the FiS kidneys were rejected within 55 days. Of 24 recipients, only 4 survived longer than 4 months. However, two-thirds of the FLF1 recipients survived longer than 4 months. The other third died with 64 days. During the first postoperation week a high level of lymphocytotoxin was detected in the serum of the FiS kidney recipients. Thereafter hardly any alternation of its titer was found, and no variation among the recipients of major histocompatible kidney allografts was shown. The FLF1 kidney recipients showed a low titer of antibody. The hemagglutinin titer showed the same trend as the lymphocytotoxin titer. A blocking serum factor could not be found in the serum of the kidney recipients with the microcytotoxity assay method or with the allorosette-formation inhibition test. Cellular immunity, which was studied with the GvH-reaction and microcytotoxity assay, was detected in the first postoperative week. However, this immunity was gradually supressed, and after 6 weeks was no longer to be found. This immunological status remained unchanged in the indefinitive surviving kidney-recipients in spite of antigen inoculation with two skin allografts of donor origin. This immunological status could be defined as "graft acceptance".