Indicating that the mechanisms observed by Wei et al. also guide regulation of gene expression and differentiation in CD8+ T cells, and indeed are relevant in vivo, we have recently showed that changes in the transcriptional profiles of CD8+ T cells differentiating in response to an acute viral infection also correlated with changes in the deposition of H3K4me3 and H3K27me3, across the stages of differentiation, including memory (6). The gene discussed is CD8A; the disease is viral infectious disease.