Tsui et al. reported that a small subset of TCF-1+CD62L+ Tpex cells are the stem-like population essential for long-term self-renewal, maintenance of Tex lineage and responsiveness to immunotherapy.356 In human individuals experienced latent infection such as CMV or EBV, TCF-1+ progenitors are comprised of two subsets based on PD-1 and TIGIT expression. This evidence concerns the gene TCF7 and disease arising from reactivation of latent virus.