Indeed, CD25 expression and STAT5 activity are augmented in LCMV infection in comparison with influenza infection.46 In the absence of T-bet during LCMV infection, the loss of IL-2 consumers (Th1 cells) results in excessive IL-2 and STAT5 activity, and thus, cells are blocked from both the Th1 and Tfh fates.46 Together, these results explain how high IL-2 may regulate Bcl6 expression to act as a cytokine switch between Tfh and Th1 fate commitment. This evidence concerns the gene IL2 and influenza.