NK cells derived from DLBCL patients produce less IFN-γ. (A-B) Subset composition of NK cells from human peripheral blood monocytes (PBMC) from healthy donors and diffuse large B-cell lymphoma (DLBCL) patients defined by expression of CD56 and CD16. (A) Representative flow cytometric plot showing the gating strategy for NK cells and NK cell subsets. (B) Frequencies of NK cell subsets (n = 13 each group). (C-D) NK cells were flow cytometry-purified from the PBMCs of healthy or DLBCL donors. NK cells were cultured with IL-2 in vitro to obtain sufficient numbers. NK cells were then cocultured with K562 cells for 6 hours at 1:1 or 1:5 effector: target ratios. (C) Frequencies of K562 target cells that were killed after coculture (n = 4-5 each group). (D) Frequencies of NK cells undergoing degranulation (CD107a⁺). (E) PBMC from healthy donors and DLBCL patients were stimulated with IL-15 + IL-12 + IL-18 for 20 hours or left unstimulated. GolgiPlug was added for the last 4 hours to stop protein release. Frequencies of IFN-γ/granzyme B (GzmB)-producing NK cells were assessed by flow cytometry (n = 13 each group). Data show mean ± SEM; statistical significance (*P < .05; NS, not significant) was determined by (B) Mann-Whitney test or by (C-E) 2-way ANOVA followed by Sidak test.