Importantly, the phenotype of the disease‐driving CD8 T cells in mice during active HLH resembles those of patients with untreated HLH, reflected by strong downregulation of CD127 on most of the cells (Ammann et al, 2017), a prominent KLRG1/CD127 double negative population and a population with high expression of inhibitory receptor PD‐1. The gene discussed is IL7R; the disease is hemophagocytic syndrome.