NK cell frequency and cytotoxicity are reduced in high-risk B/T-ALL patients. (A) CyTOF analysis depicting frequencies of total CD56⁺ HLA-DR⁻ NK cells (after gating out CD14⁺ and/or CD33⁺ monocytes, and then CD3⁺ T cells, and then CD19⁺ and/or CD20⁺ B cells, referred to as nonmonocyte non-T non-B gate) in BMMCs and PBMCs of patients with B/T-ALL (n = 12 BMMC; n = 8 PBMC) and healthy donors (n = 12 BMMC; n = 10 PBMC). Data are median ± interquartile range. (B) Representative viSNE plots showing surface CD56 expression in the non–T-cell, non–B-cell, nonmonocyte, HLA-DR⁻ population in BMMCs and PBMCs from healthy donors and patients with B/T-ALL. The color scale represents the intensity of CD56 expression on each cell. Flow cytometry density plots and comparison of NK cell–specific cytotoxicity of sorted CD3⁻CD56⁺ NK effector cells from PBMCs of healthy donors (n = 3) and patients with B-ALL (n = 3) after coculture with the commonly used K562 erythroleukemia NK cell–sensitive target for measuring NK cell function (C) or NK cell–sensitive MOLT-4 T-ALL target cells (D) for 5 hours at an effector-to-target ratio of 10:1. Data are shown from 3 independent experiments; each experiment was conducted using the same number of NK cells sorted from 1 patients with B-ALL and 1 healthy donor. Each experimental pair is connected by a line. The exact P value was calculated using the paired Student t test.