Fig. 2. MDSCs from HCV patients promote Foxp3⁺ T_FR cell differentiation and suppress IFN-γ expression by Teff cells.

a Correlation of MDSCs with T_FR/T_FH cells in peripheral blood of HCV patients. The frequencies of MDSC (CD14⁺CD33⁺HLA-DR⁻), T_FR (CD4⁺CXCR5⁺Foxp3⁺) and T_FH (CD4⁺CXCR5⁺Foxp3⁻) cells in PBMCs of 9 HCV-infected patients were simultaneously examined by flow cytometry, and then analyzed by Pearson Correlation. R and P values are shown above the summary data. b CD33⁺ myeloid cells from HCV patients induce T_FR cell generation. Healthy PBMCs were co-cultured with or without CD33⁺ myeloid cells derived from HCV patients for 5 days, followed by flow cytometric analysis for the percentage of T_FR cell (CD4⁺CXCR5⁺Foxp3⁺) frequency in lymphocytes. c Reducing T_FR cells, but not T_FH cells, by depletion of CD33⁺ myeloid cells from PBMCs derived from HCV patients. HCV-derived PBMCs, with or without MDSC depletion, were cultured in vitro for 5 days, followed by flow analysis for CD4⁺CXCR5⁺Foxp3⁺ T_FR and CD4⁺CXCR5⁺Foxp3⁻ T_FH cells. d Representative dot plots and summary data of flow cytometric analysis of IFN-γ production by CD4⁺ cells in PBMCs with or without CD33⁺ myeloid cell depletion. e Depletion of CD33⁺ myeloid cells from PBMCs of HCV patients improves IFN-γ production by T follicular cells, T_FR and T_FH cells. HCV PBMCs, with or without CD33⁺ myeloid cell depletion, were cultured ex vivo in the presence of stimulation for 5 days, followed by immune staining and flow analysis for IFN-γ production by CD4⁺CXCR5⁺ T follicular cells as well as CD4⁺CXCR5⁺Foxp3⁺ T_FR and CD4⁺CXCR5⁺Foxp3⁻ T_FH cells. f Depletion of CD33⁺ myeloid cells from PBMCs of HCV patients reduces IL-10 production by T follicular cells and T_FR cells, but not by T_FH cells. PBMCs isolated from chronic HCV patients, with or without depletion of CD33⁺ myeloid cells, were cultured ex vivo in the presence of anti-CD3/CD28 stimulation, followed by flow cytometric analysis for IL-10 expression in CD4⁺CXCR5⁺ T cells as well as CD4⁺CXCR5⁺Foxp3⁺T_FR and CD4⁺CXCR5⁺Foxp3⁻ T_FH cells. P values are shown above each panel