Fig. 5

Induction of arginase 1 for MDSC-mediated CD8⁺ T-cell suppression being Trem2 dependent. A Schema of study design. B, C mRNA transcriptional level of Trem2 and Arg1 in BM-MDSCs from WT or Trem2 KO mice; data being presented as fold change relative to the GAPDH mRNA transcriptional level. D–G CFSE-labeled splenocytes from naïve mice being co-cultured with 12% of WT or Trem2 KO BM-MDSCs in the presence of L-arginine or CB-1158 (inhibitor of Arg1) for an additional two days; proliferation being assessed by flow cytometry, and histograms of proliferated population being gated on CD8⁺ T cells; data from two representatives of three reproducible experiments; Mean ± SEM of each group being presented in results (n = 6); for comparisons between two subgroups, differences being evaluated by Mann–Whitney nonparametric test: * (P < 0.05), ** (P < 0.01), or *** (P < 0.001); when comparing to the sole CD8.⁺ T subgroup (without MDSCs, CB1158, and L-arginine), differences being demonstrated as # (P < 0.05), ## (P < 0.01), or ### (P < 0.001) according to the Mann–Whitney nonparametric test. Arg1, arginase 1; BM, bone marrow; MDSCs, myeloid-derived suppressor cells; WT, wild-type; TR2KO, Trem2 knockout; Trem2, triggering receptors expressed on myeloid cells 2