Fig. 8.

IFN-γ produced by Th1-like Tfh cells is required in a B cell-intrinsic manner for IgG2c antibody class switching. a–d CD45.1⁺ WT: Ifngr1^−/− mixed bone marrow chimeras were administered with anti-IFNAR1 antibody 1 day prior to ZIKV infection. Splenocytes were collected on 14 dpi for measurement of Tfh cell and antibody responses (n = 5). a Representative flow cytometry plots of CXCR5^highPD-1^high cells and CXCR5^mediumPD-1^medium cells were presented as Tfh cells and pre-Tfh cells (Left panel); summary of the percentages of these cells (right panel). b Representative flow cytometry data of IFN-γ staining in splenic WT (CD45.1⁺) Tfh cells and Ifngr1^−/− (CD45.2⁺) Tfh cells at day 14 after ZIKV infection (left panel); summary of the percentages of WT or Ifngr1^−/− IFN-γ⁺ Tfh cells (Right panel). c, d Representative flow cytometry data of IgG2c (c) and IgG1 (d) intracellular staining in B220^lowCD138⁺IgD^low cells (left panel); summary of the percentages of these cells (Right panel). e–i WT: Bcl6^fl/flCd4-Cre chimeras, and Ifng^−/−: Bcl6^fl/flCd4-Cre chimeras were administered with anti-IFNAR1 antibody one day prior to ZIKV infection (n = 5 for WT: Bcl6^fl/flCd4-Cre group and n = 3 for Ifng^−/−: Bcl6^fl/flCd4-Cre group). e Representative flow cytometry plots of CXCR5^highPD-1^high cells and CXCR5^mediumPD-1^medium cells were presented as Tfh cells and pre-Tfh cells (left panel); bar graphs summarized the percentages of these cells (right panel). f Representative flow cytometry plots of IFN-γ⁺ cells in CD4⁺CXCR5⁻ T cells were presented as Th1 cells (left panel); bar graphs summarized the percentages of Th1 cells (right panel). g Representative flow cytometry plots of IFN-γ staining in CXCR5^highPD-1^high Tfh cells (left panel); the percentages of IFN-γ⁺ Tfh cells were summarized by bar graphs (right panel). h Representative flow cytometry data of IgG2c intracellular staining in B220^lowCD138⁺IgD^low splenocytes (left panel); bar graphs summarized the percentages and numbers of IgG2c⁺ cells (right panel). i The concentrations of ZIKV envelope specific IgG2c antibodies in chimeras were measured by ELISA. The summary data were presented as mean ± SEM. Statistical differences were determined by Student’s t test and p values were indicated by *p < 0.05, or **p < 0.01, or ***p < 0.001. Data (a–i) are pooled from two independent technical duplicates. Source data are provided as a Source Data file