Inflammasome induction in MDSC associated with loss of Arg1 expression. MDSC-IL13 were induced for NLRP3 or AIM2 inflammasomes as indicated, washed extensively, and replated in complete media overnight. (A) Enzymatic activity of cell-associated arginase for wild-type or (B) ASC^−/− MDSCs, normalized to total cell number. Data are pooled from 2 independent experiments. MDSCs generated from YARG mice, followed by in vitro induction of inflammasomes (as previously discussed) and replating in complete media. (C) YFP fluorescence for CD11b-gated MDSCs after 2 additional days in culture indicated as representative histograms (shaded histogram represents unstimulated BM from YARG donor) and (D) summary data of % YFP⁺. (E) YFP detection for MDSC-IL13 recovered from day 5–transplanted animals with BM only (no GVHD) or BM plus whole T cells (GVHD). YARG BM (YFP-Arg1 bone marrow) indicates baseline YFP fluorescence. (F) IL-1β production before and after NLRP3 (ATP + LPS) inflammasome activation for bulk MDSC-IL13 or sorted granulocytic Ly6G⁺C⁺ (Ly6G⁺) and monocytic Ly6C⁺ subsets. (G) CFSE proliferation of anti-CD3ε driven CD8⁺ B6 T cell responses in the presence of sorted granulocytic (Ly6G⁺) or monocytic (Ly6C⁺) subsets of MDSC-IL13 at a 1:1 ratio. (H) Cell-associated arginase bioactivity for bulk MDSC-IL13 and sorted granulocytic (Ly6G⁺) or monocytic (Ly6C⁺) subsets. The dashed line indicates background activity for Arg1-deficient splenocytes. Data regarding MDSC subsets are representative of 3 independent experiments.