Specifically, we observed significant decreases in NK cells, NKT cells, Tregs, CD4+ TCM cells, CD8+ TEMRA cells, and CD56dimCD16+ NK cells in patients with HLH, accompanied by an increase in Tnaive cells and in the less differentiated CD56brightCD16− and CD56dimCD16− NK subsets. Here, CD4 is linked to hemophagocytic syndrome.