IL21 and infection: IL-21+ TFH and IL-21− TFH cells were transcriptionally distinct (Extended Data Fig. 6a); however, across infections, the intersection of similarly regulated genes revealed only Ly6c2, Il7r (encoding CD127), and Sell (encoding CD62L), were downregulated in the IL-21+ TFH population in four of five infections (Extended Data Fig. 6a).