Neonatal NK cells are functionally educated by autologous HLA class I ligands. CD107 mobilization against K562 was measured in single-KIR2DL1⁺ and single-KIR2DL2/3⁺ NK cells from CB of C1/C1 (A) and C2/C2 (C) donors and similarly in PB of C1/C1 (B) and C2/C2 (D) donors. In each case, data are shown as individual frequencies with statistical significance calculated for the ratio of KIR2DL1 to KIR2DL2/3 (left side) and as box plots (right side). Boxes represent the median and 25th/75th percentiles; and whiskers, the lowest and highest data points without outliers (stars, open circles). Statistical significance was determined by 2-tailed t test: *P < .05, **P < .01, and ***P < .001. The sample distribution was C1/C1 (n = 10) and C2/C2 (n = 15) for CB and C1/C1 (n = 14) and C2/C2 (n = 6) for PB. (E) Changes in frequency of CD107-mobilizing single-KIR2DL1⁺ (light gray) and single-KIR2DL2/3⁺ (dark gray) NK cells of CB donors. Donors were the same as in panels A and C but including C1/C2 (n = 25) donors. Throughout the figure, functional analysis was done without further subdivision into KIR haplotype groups. Values represent the mean, and error bars represent the SD. (F) Production of IFN-γ in NK cells from CB after 6-hour coculture with K562. Donors were divided into C1/C1 (n = 8), C1/C2 (n = 25), and C2/C2 (n = 11) subgroups. Box plots represent the ratio between IFN-γ-producing single-KIR2DL1⁺ and single-KIR2DL2/3⁺ NK cells. P values were calculated by analysis of variance: *P < .05, **P < .01, and ***P < .001.