Human gamma delta(+) T lymphocytes have in vitro graft vs leukemia activity in the absence of an allogeneic response

Refractory acute lymphoblastic leukemia (ALL) is often incurable, and relap se rates following allogeneic bone marrow transplantation (BMT) remain high . We have reported that patients who develop increased numbers of gamma del ta (+) T cells soon after BMT are significantly less likely to relapse, We now show in seven donor/recipient pairs that donor-derived V delta1(+)CD4(- )CD8(-)gamma delta (+) T cells are activated and proliferate in response to recipient primary ALL blasts, In addition, these cells have been shown to bind and lyse the recipient ALL blasts, Separately, gamma delta (+) T cells proliferate poorly or not at all in mixed lymphocyte culture against HLA-m ismatched unrelated stimulator cells. These observations suggest that allog eneic gamma delta (+) T cells could be an effective immunotherapeutic strat egy against refractory disease without the risk of graft-versus-host diseas e.