Human Vδ1 γδ T cells expanded from peripheral blood exhibit specific cytotoxicity against B-cell chronic lymphocytic...

There is increasing interest in using γδ T cells (GDTC) for cancer immunotherapy. Most studies have been concerned with the Vδ2 subset in blood, for which several expansion protocols exist. We have developed a protocol to expand Vδ1 and Vδ2 preferentially from human blood. We have characterized these subsets and their specificities for leukemic targets.

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.

Longer initial exposure to Con A typically resulted in higher Vδ1 prevalence. Vδ1 were activated by and cytotoxic to B-cell chronic lymphocytic leukemia (B-CLL)-derived MEC1 cells, whereas Vδ2 also responded to MEC1 but more so to the Philadelphia chromosome-positive [Ph+] leukemia cell line EM-enhanced green fluorescent protein (2eGFPluc). Vδ2 clone cytotoxicity against EM-2eGFPluc correlated with Vδ2 T-cell antigen receptor (TCR) and receptor found on Natural Killer cells and many T-cells (NKG2D), whereas Vδ1 clone cytotoxicity versus MEC1 correlated with Vδ1 TCR, CD56 and CD95 expression. Vδ1 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).

Our ability to expand peripheral Vδ1 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.