BCL6 and influenza: We found that heterologous influenza rechallenge resulted in significant increases in the numbers of polyclonal effector antigen-specific CXCR5– Th1 cells in both rGP- and LCMV-primed mice, as well as CXCR5+BCL6+ GC Tfh cells in LCMV-primed mice compared to primary influenza infection.