ENHANCEMENT OF BM ALLOGRAFTING FROM C57BL 6 NUDE-MICE INTO C3H/HEJ RECIPIENTS BY TOLERIZED T-CELLS FROM (C57BL/6-]C3H/HEJ) AND (C3H/HEJ-]C57BL/6) CHIMERAS/

The possible participation of T cells in the promotion of hematopoieti c engraftment of BM allografts, as opposed to their potential role in overcoming host-versus-graft reactions, was investigated recently by u sing (host X donor)F1 T cells devoid of graft-versus-host activity. In the present study, we provide further evidence of this effect by usin g tolerized thymocytes from established allogeneic chimeras. We show t hat tolerant mature thymocytes from donor type (C57BL/6 --> C3H/HeJ) o r host type (C3H/HeJ --> C57BL/6) chimeras are as effective as (donor x host)F1 thymocytes in promoting both short-term and long-term engraf tment of C57BL/6-Nu/Nu T cell-depleted BM cells in lethally irradiated C3H/HeJ recipients.