Fig 2: MDSCs and IL10 are increased in 0.5Gy-exposed mice.Mice were exposed to either 0.5 Gy or 5 Gy total body irradiation and analyzed seven days later. Representative dot plots of the gating strategies. A The population of CD11b+ /GR1+ cells. B gMDSCs (CD11b+ , Ly6G+, and Ly6Clow) and mMDSCs (CD11b+ , Ly6G-, and Ly6Chigh) from the spleens and intestines of irradiated mice were identified and analyzed by flow cytometry. C Representative dot plots of the gating strategy used to identify IL10+ cells. IL10+ cells were gated and the proportions of CD11b+ /GR1+ cells. These cells were gated on gMDSCs (CD11b+ , Ly6G+, and Ly6Clow) and mMDSCs (CD11b+ , Ly6G-, and Ly6Chigh) cells were evaluated from mouse spleens and intestines. D Representative immunofluorescence images of cells from spleen stained for GR1 (green), IL10 (red), and GR1/IL10 (yellow). DAPI staining (blue) was used to determine the number of nuclei. Scale bar = 100 µm. The data are represented as mean ± SD (n = 8). **P < 0.01, ***P < 0.001 vs. control.

Fig 3: Depletion of mMDSCs exacerbates radiation-induced intestinal inflammation.Mice were tail-vein injected with either anti-IgG, anti-Ly6G, or anti-Ly6C (250 µg/mouse) four times per week after irradiation. All the results were determined 21 days after irradiation. A Photomicrographs of colon sections, histological grades, and body weights after depletion of Ly6G or Ly6C. Scale bar = 100 µm. B The relative expression of cytokines (IL10, TGFß, IL6, IFN?, IL1ß, and TNFa) in the intestines of irradiated mice were measured by qRT-PCR. The data are represented as mean ± SD (n = 8). *P < 0.05, **P < 0.01, ***P < 0.001 vs. IR + IgG. IR irradiation.

Fig 4: Radiation increases intestinal inflammation that is accompanied by MDSC expansion.Mice were exposed to 7.5 Gy for 1 week to induce intestinal inflammation. A Photomicrographs of colon sections, histological grades, colon lengths, body weights, and survival rates for mice 21 days after irradiation. Scale bar = 100 µm B Representative dot plots of the gating strategy used to identify CD11b+ /GR1+ cells from the spleens and intestines of mice 21 days after irradiation. C Representative immunofluorescence images of spleen and intestine stained for CD11b (green), GR1 (red), and CD11b+ /GR1+ (yellow) cells. DAPI staining (blue) was used to determine the number of nuclei. Scale bar = 100 µm D CFSE-labeled CD3+ T cells were co-cultured with splenic MDSCs and stimulated using anti-CD3 and anti-CD28 monoclonal antibodies. The cells were harvested and analyzed after 7 days. CFSE dilution demonstrated that T-cell proliferation was inhibited by MDSCs (left) and that this inhibition occurred in a dose-dependent manner (right). E The two MDSC subtypes, namely gMDSCs (CD11b+ , Ly6G+, and Ly6Clow) and mMDSCs (CD11b+ , Ly6G-, and Ly6Chigh), were identified and analyzed by flow cytometry from spleen and intestine samples. The data are represented as the mean ± SD (n = 8). *P < 0.05, **P < 0.01, ***P < 0.001 vs. control. IR irradiation.