Lack of CTL activity in human CHS patients correlates with early-onset HLH. (A-C) Cytotoxicity of freshly isolated NK cells from CHS patients was analyzed on ⁵¹Cr-labeled K562 target cells. (D-F) Cytotoxicity of CTL after generation of phytohemagglutinin/IL-2 blasts generated from CHS patients was analyzed in an anti-CD3 redirected-lysis assay on L1210 target cells. (A,D) Patients with early-onset HLH (before age 3). (B,E) Patients with late-onset HLH (age 3 or later). (C,F) Patients who never developed HLH. Gray areas represent the range between the 10th and 90th percentile of values obtained with NK cells (A-C) or CTLs (D-F) from healthy donors.