NK-cell number and correlation with CTCL patient survival. (A) Absolute NK-cell numbers were calculated in normal donors (n = 51; mean ± standard error of the mean [SEM], 0.2442 ± 0.02 ) and CTCL patients (n = 121; 0.208 ± 0.01; P = .08). (B) Kaplan-Meier curves for overall survival at possible absolute NK-cell counts in CTCL patients (n = 121). (C) NK cells, CD56⁺/lineage (CD3/CD14/CD20), were isolated from freshly obtained peripheral blood samples from CTCL patients and normal control donors. (D) Purified NK cells were co-cultured with K562 leukemic targets in a standard chromium release assay at indicated ratios. Data are presented as mean ± SEM. *P ≤ .05; **P ≤ .01; ***P ≤ .001; unpaired 2-tailed Student t test. FSC, forward scatter; ns, not significant; SSC, side scatter.