The phenomenon that few T cell clones dominate antigen‐specific responses and that individual clones consist of ‘T cell family members’ with highly diverse properties had previously been reported for murine CD4 and CD8 T cells responding to infections using other technologies8, 9, 12, 13, 14, 15, 55 (see barcoding, single cell transfer), and these single‐cell RNA‐sequencing‐based studies extend this concept to human tumour‐, allergen‐ and vaccine antigen‐reactive T cells. This evidence concerns the gene CD8A and infection.