Immunosuppressive effect of syngeneic thymus cells on allograft rejection.

Transfer of thymus cells from young chickens to syngeneic recipients suppresses the allograft rejection between strains differing at the major histocompatibility (B) locus. Thymus cell transfer in combination with a light whole body irradiation (360 R) prolongs significantly the mean rejection time of skin allografts and leads in a proportion of recipients to long-lasting graft survival (greater than 200 days). Three weeks after the cell transfer, the suppression appears to be antigen specific, as judged by the normal reactivity against third-party skin grafts. From the types of thymus cells preparations that are effective in these experiments, it is inferred that the suppressor cell is a bursa-dependent lymphocyte, which is predominantly found in the young chicken thymus and which is different from B-lymphocytes, B-precursor cells, or graft-versus-host-reactive T-cells.