MAF and infection: Subsequently, in the PR8 infection model, we found that whereas the c-Maf deletion by CRISPR/Cas9 (c-Maf-CRISPR) in naïve CD4+ T cells negatively affected the overall CXCR5+ Tfh cell development (with increased non-Tfh cell percentages) (Fig. 6g), still a robust population of CXCR5+CD4+ T cells was generated at the peak of the CD4+ T cell response (Fig. 6g).