Allogeneic bone marrow cells that facilitate complete chimerism and eliminate tumor cells express both CD8 and T-cell antigen receptor-αβ

Nonmyeloablative host conditioning regimens have been used in clinical allogeneic bone marrow and hematopoietic progenitor transplantation to effectively treat lymphohematopoietic tumors and reduce early toxicity. However, severe graft-versus-host disease (GVHD) remains a major problem. The goal of the current study was to determine whether specific subsets of cells in allogeneic bone marrow transplants can effectively treat the BCL₁ B-cell lymphoma in nonmyeloablated BALB/c mouse hosts given a single dose of sublethal (450 cGy) total body irradiation, without inducing severe GVHD. The experimental results show that high doses of whole bone marrow cells from major histocompatiblity complex (MHC)-mismatched donors eliminate both normal and malignant host-type lymphohematopoietic cells without causing injury to nonlymphohematopoietic host tissues. The CD8⁺T-cell antigen receptorαβ⁺ (TCRαβ⁺) T cells within the marrow transplants mediated the killing of the tumor cells via both perforin- and FasL-dependent pathways. Cells present in marrow transplants from either CD8^-/- or TCRα^-/- donors failed to eliminate malignant and normal host lymphohematopoietic cells. Addition of small numbers of blood mononuclear cells to the marrow inoculum caused lethal GVHD. Thus, the resident allogeneic bone marrow CD8⁺ TCRαβ⁺ T cells had the unique capacity to eliminate the host lymphohematopoietic cells without nonlymphohematopoietic tissue injury.