THE EFFECT OF INJECTION OF DONOR BONE-MARROW ON THE FREQUENCY OF DONOR-REACTIVE CTL IN ANTILYMPHOCYTE-SERUM TREATED, GRAFTED MICE

The survival of C3H/He skin grafts can be prolonged on B6AF1 mice immunosuppressed with ALS by the injection of C3H/He marrow 1 week postgrafting. The precursor frequencies of donor-reactive CTL in the spleen and lymph nodes of ALS-treated, grafted mice given donor marrow were compared with CTL frequencies observed in ALS-treated, grafted controls. Spleens and nodes were removed from experimental and control mice on days +8, +14, +21, +58, and 1 year postgrafting, and used as effectors in the LDA. Donor-reactive CTL in the marrow-injected group remained suppressed as long as the recipients maintained their grafts. The frequency of CTL to third-party antigens was normal in mice bearing long-term C3H/He grafts. When marrow-injected mice rejected their grafts, the total donor-reactive CTL frequency returned to normal. In contrast, in ALS-treated controls that did not receive marrow, the total number of donor-reactive CTL returned to normal levels with recovery from the immunosuppressive effects of ALS. These results suggest that donor marrow suppresses the regeneration of donor-reactive CTL in the lymphoid tissues of ALS-treated mice, possibly by veto cell activity.