The lymphoma microenvironment suppresses NK cell cytokine production. (A-C) C57BL6/J mice were inoculated IV with GFP+ Eµ-myc lymphoma cells (1 × 105 cells). NK cells derived from spleens and bone marrows of Eµ-myc lymphoma bearing or healthy mice were analyzed on days 14 through 18 after inoculation. (A) Abundance of NK cells in spleen and bone marrow (n = 7) and (B) proportions of mature NK cell subsets were measured by CD11b and CD27 expression on NK cells derived from healthy and Eµ-myc lymphoma spleen (n = 11). (A) Numbers in the representative plots denote the percentages of populations of the parental gates. (D) Analysis of splenic NK cells derived from Eµ-myc lymphoma-bearing or healthy mice were analyzed on 14 days after inoculation to assess expression of TIGIT (n = 4-5). (E-F) IL-12 and IL-18 were administered to healthy and Eµ-myc lymphoma-bearing mice on day 17 after lymphoma inoculation. Splenocytes were harvested 20 hours later and treated with GolgiPlug for 4 hours to stop cytokine release before flow cytometric analysis of intracellular cytokine production (n = 5). (E) The percentages of cytokine IFN-γ-producing NK cells, and (F) Δ mean fluorescent intensity (ΔMFI, MFI of staining Ab minus MFI of respective isotype Ab) of IFN-γ of cytokine-producers are shown. Numbers in the representative plots denote the percentages of IFN-γ-producing NK cells. (G) α galactosylceramide (αGC) was administered to healthy and Eµ-myc lymphoma-bearing mice on day 14 after lymphoma inoculation. Splenocytes were harvested 20 hours later and treated with GolgiPlug for 4 hours before flow cytometric analysis. IFN-γ (left) and GzmB (right) were assessed by flow cytometry (n = 8). Data show mean ± SEM; statistical significance (*P < .05; **P < .01; ***P < .001; ****P < .0001; NS, not significant) was determined by Mann-Whitney test.