Cellular basis of graft versus host tolerance in chimeras prepared with total lymphoid irradiation.

Abstract

BALB/c mice given allogeneic (C57BL/Ka) bone marrow cells after total lymphoid irradiation become stable chimeras with .apprx. 80% donor-type and 20% host-type cells in the spleen. The chimeras do not develop graft vs. host disease (GVHD). Purified cells of C57BL/Ka origin from the chimeras mediated GVHD in lightly irradiated C3H (3rd party) but not in BALB/c (host-strain) mice. Graft vs. host tolerance in the chimeras could not be explained by complete immunodeficiency of donor-type cells, serum blocking factors or suppressor cells of host (BALB/c) origin. Clonal deletion or suppression of lymphocytes reactive with host tissues remain possible explanations. The transfer of donor-type chimeric spleen cells to BALB/c recipients given 500-550 rad whole-body irradiation led to stable mixed chimerism in .apprx. 50% of recipients. The cells were presumably acting as tolerogens because similarly irradiated BALB/c mice given (BALB/c .times. C57BL/Ka)F1 spleen or bone marrow cells became stable mixed chimeras.