Fig. 6.

Th1-like Tfh cell is required for IgG2c antibody class switching. Mixed bone marrow chimeras (WT: Bcl6^fl/flCd4-Cre; and Tbx21^−/−: Bcl6^fl/flCd4-Cre) were administered with anti-IFNAR1 antibody one day prior to ZIKV infection. Splenocytes and sera were collected on 14 dpi for measurement of Tfh cell and antibody responses, respectively (n = 5 for WT: Bcl6^fl/flCd4-Cre group and n = 4 for Tbx21^−/−: Bcl6^fl/flCd4-Cre group). a 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 in each group (right panel). b Representative flow cytometry plots of CXCR5^highPD-1^high cells and CXCR5^mediumPD-1^medium in CD4⁺CD44^highCD62L^low T cells were presented as Tfh cells and pre-Tfh cells (left panel); bar graphs summarized the percentages of cells in each group (right panel). c Representative flow cytometry plots of IFN-γ staining in CXCR5^highPD-1^high Tfh cells (left panel); the percentages and numbers of IFN-γ⁺ Tfh cells were summarized by bar graphs (right panel). d Representative flow cytometry plots of IgG1 and IgG2c intracellular staining in B220^lowCD138⁺IgD^low cells (Left panel); bar graphs summarized the percentages and numbers of IgG1⁺ and IgG2c⁺ cells (right panel). e The concentrations of ZIKV envelope specific IgG1 and 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–e) are pooled from two independent technical duplicates. Source data are provided as a Source Data file