γδ T lymphocytes increase hIgG1-induced activation of NK cells. (A) Purified natural killer (NK) cells and isopentenylpyrophosphate plus interleukin-2 (IPP+IL-2) expanded γδ T lymphocytes were cocultured at a 4:1 ratio in the presence or absence of plate-immobilized human immunoglobulin G1 (hIgG1; 2.5 μg/mL) for 48 hours. The expression of CD69 was analyzed by flow cytometry. Histograms represent gated CD3⁻CD56⁺ NK cells. An example of gating strategy is shown in supplemental Figure 1. (B) Purified NK cells (2 × 10⁵ cells/well) were cultured with indicated numbers of IPP+IL-2 expanded γδ T lymphocytes in the presence of immobilized hIgG1 (2.5 μg/mL) for 48 hours. Expression of activation markers CD69 and CD54 were assessed by flow cytometry and plotted as a percentage of CD69 and CD54 positive gated NK cells. Representative data from 1 of 10 independent experiments is shown.