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Donor CD8+ T Cells Mediate Graft-versus-Leukemia Activity without Clinical Signs of Graft-versus-Host Disease in Recipients Conditioned with Anti-CD3 Monoclonal Antibody1

Donor CD8+ T cells play a critical role in mediating graft-vs-leukemia (GVL) activity, but also induce graft-vs-host disease (GVHD) in recipients conditioned with total body irradiation (TBI). In this study, we report that injections of donor C57BL/6 (H-2b) or FVB/N (H-2q) CD8+ T with bone marrow cells induced chimerism and eliminated BCL1 leukemia/lymphoma cells without clinical signs of GVHD in anti-CD3-conditioned BALB/c (H-2d) recipients, but induced lethal GVHD in TBI-conditioned recipients. Using in vivo and ex vivo bioluminescent imaging, we observed that donor CD8+ T cells expanded rapidly and infiltrated GVHD target tissues in TBI-conditioned recipients, but donor CD8+ T cell expansion in anti-CD3-conditioned recipients was confined to lymphohematological tissues. This confinement was associated with lack of up-regulated expression of α4β7 integrin and chemokine receptors (i.e., CXCR3) on donor CD8+ T cells. In addition, donor CD8+ T cells in anti-CD3-conditioned recipients were rendered unresponsive, anergic, Foxp3+, or type II cytotoxic T phenotype. Those donor CD8+ T cells showed strong suppressive activity in vitro and mediated GVL activity without clinical signs of GVHD in TBI-conditioned secondary recipients. These results indicate that anti-CD3 conditioning separates GVL activity from GVHD via confining donor CD8+ T cell expansion to host lymphohemological tissues as well as tolerizing them in the host.