Human Vδ1 γδT cells expanded from peripheral blood exhibit specific cytotoxicity against B-cell chronic lymphocytic leukemia-derived cells

Background aims. There is increasing interest in using gamma delta T cells (GDTC) for cancer immunotherapy. Most studies have been concerned with the V delta 2 subset in blood, for which several expansion protocols exist. We have developed a protocol to expand V delta 1 and V delta 2 preferentially from human blood. We have characterized these subsets and their specificities for leukemic targets. Methods. GDTC were isolated from the peripheral blood mononuclear cells (PBMC) of healthy donors via positive magnetic cell sorting; their proliferation in vitro was induced by exposure to the mitogen concanavalin A (Con A). CD107 and cytotoxicity (Cr-51-release and flow cytometric) assays were performed. GDTC clones and target cells were immunophenotyped via flow cytometry. Results. Longer initial exposure to Con A typically resulted in higher V delta 1 prevalence. V delta 1 were activated by and cytotoxic to B-cell chronic lymphocytic leukemia (B-CLL)-derived MEC1 cells, whereas V delta 2 also responded to MEC1 but more so to the Philadelphia chromosome-positive [Ph+] leukemia cell line EM-enhanced green fluorescent protein (2eGFPluc). V delta 2 clone cytotoxicity against EM-2eGFPluc correlated with V delta 2 T-cell antigen receptor (TCR) and receptor found on Natural Killer cells and many T-cells (NKG2D), whereas V delta 1 clone cytotoxicity versus MEC1 correlated with V delta 1 TCR, CD56 and CD95 expression. V delta 1 also killed Epstein-Barr Virus (EBV)-negative B-CLL-derived TMD2 cells. Immunophenotyping revealed reduced HLA-ABC expression on EM-2eGFPluc, whereas MEC1 and TMD2 exhibited higher Tumor Necrosis Factor-Related Apoptosis-Inducing Ligand (TRAILR1). Conclusions. Our ability to expand peripheral V delta 1 cells and show their cytotoxicity to B-CLL-derived cell lines suggests that this novel approach to the cellular treatment of B-CLL may be feasible.