B-cell lymphoma leads to elevation of fatty acid levels associated with repressed NK cell function. (A) Plasma samples were collected from healthy and Eµ-myc lymphoma-bearing mice on day 7 and 13 days after lymphoma inoculation, and plasma fatty acid (FA) levels including myristic acid, palmitic acid (PA), palmitoleic acid, steric acid (SA), oleic acid (OA), linoleic acid (LA), and linolenic acid were measured using liquid chromatography mass spectrometry (LC-MS) (n = 10-14). (B) Splenic NK cells were isolated and expanded in culture for 10 days with IL-15, after which they were either pretreated with IL-15 + 400 µM of PA, SA, OA, LA, or bovine serum albumin (BSA) control, or (C) IL-15 + increasing amounts of PA or BSA control for 48 hours, followed by 20 hours stimulation with IL-12 + IL-15 + IL-18 in the presence of FAs. GolgiPlug was added for the last 4 hours to stop protein release. Expression of IFN-γ, TNF, and GzmB was assessed by flow cytometry (n = 4-8). (D) Human PBMCs were pretreated with PA for 4 hours, followed by cytokine stimulation and measurement of expression of IFN-γ and GzmB (n = 13). (E) Mouse NK cells were pretreated with IL-15 + 4 FAs combined (100 µM of PA, SA, OA, and LA) or BSA control for 48 hours, followed by cytokine stimulation and measurement of expression of IFN-γ, TNF, and GzmB as in D (n = 4-7). Fold changes (FC) were calculated as δ MFI (MFI of target Ab staining minus MFI of isotype control staining) relative to that of BSA control. Data show mean ± SEM; statistical significance (*P < .05; **P < .01; ***P < .001; ****P < .0001; NS, not significant) was determined by 2-way ANOVA followed by (A) Sidak test, (B-C) 1-way ANOVA followed by Dunnett test, (D) Wilcoxon test, or (E) Mann-Whitney test.