Future work is needed to characterize permissive versus repressive epigenetic marks (for loci of lineage-associated cytokines, effector molecules, and transcription factors) in antigen-specific memory Tfh, Th1, Th2, and Th17 cells, providing needed insight into the plasticity versus commitment of memory CD4 T cell subsets induced by infection and immunization. Here, CD4 is linked to infection.