γδ T lymphocytes induce NK cell–mediated cytotoxicity against various tumor cell lines. (A) Purified NK cells were cultured with bulk IPP-expanded peripheral blood mononuclear cells (PBMCs) at a 2:1 ratio for 48 hours (ie, 2 NK cells/1 IPP-expanded PBMC). IPP-expanded PBMCs in these experiments contained 70% to 80% γδ T lymphocytes, so the actual ratio of NK cells to IPP-expanded γδ T lymphocytes was approximately 2:0.8. NK cells were repurified from the cultures by immunomagnetic depletion of non-NK cells. Representative dot plots of NK + γδ T cells (right) and NK cells purified after 48 hours of culture (left) are shown. (B) Cytolytic activity of NK cells purified after coculture with expanded γδ T cells and immobilized hIgG1 (2.5 μg/mL) for 48 hours was analyzed in a standard 4-hour ⁵¹Cr-release assay against indicated tumor targets. Data are presented as mean ± SD of triplicate samples and are representative of 7 independent experiments. *P < .05 compared with NK cells cultured with hIgG1 alone.