Fig. 7

Immunosuppressive MDSCs recruited by elevated IL-17A after sub-chronic exposure to PM. A Gating strategy of the flow cytometry for MDSCs detection (CD11b⁺Gr-1⁺ cells) in the bone marrow and lung tissues from 8-week and 16-week PM exposed groups and their corresponding control groups. The gated CD11b⁺Gr-1⁺ cells show an increasing MDSCs proportion in both bone marrows and lung tissues following 8-week and 16-week PM exposure. B–D The proportions of MDSCs detected in the viable cells of bone marrows (B), lung tissues (C) and spleens (D) in control and PM exposed groups from WT and IL-17A^−/− mice (N = 4). E, F Immunosuppressive effects of MDSCs derived from 16-week PM exposed group on T cell proliferation (%) appeared after coculturing MDSCs derived from bone marrow (E) and lung (F) with T cells at the ratio of 1:2 in vitro. (G-H) TGF-β levels in the supernatant of the coculture system after splenic T cells were cocultured with MDSCs from bone marrow (G) and lung (H) for 72 h. The experiment was carried out in 3 replicates. The results are presented as mean ± SD. *P < 0.05; **P < 0.01; ***P < 0.001 PM-exposed mice compared with the control mice (WT⁻-PM vs WT-Con). ^#P < 0.05 compared with the WT PM-exposed mice (IL-17A^−/−-PM vs WT-PM). ^###P < 0.05 compared with the WT PM-exposed mice (IL-17A^−/−-PM vs WT-PM). Con: control group; Exp: PM exposure group