EL08.1D2 stroma and HDC increase the NKp frequency in the CD34⁺ UCB fraction. (A) Semi-log plot presenting the results of a limiting dilution experiment with CD34⁺ HPCs cultured in cytokines alone (◇, long-dashed line), cytokines and HDC (■, gray line), cytokines and stroma (▴, black line), and cytokines and HDC and stroma (○, short-dashed line). Data for a single donor are shown and are representative of 8 donors tested. The steeper slope of regression line indicates increasing NKp frequency in different conditions. (B) NKp frequency/10⁶ CD34⁺ HPCs cultured in the above-described conditions (n = 8 donors). Groups showing significant differences are indicated by asterisks (***P < .001, **P = .001-.01, and *P = .01-.05), by repeated-measures analysis of variance on log-transformed values with Bonferroni posttest. (C) Results of microscopic scoring of cell density in limiting dilution experiment at day 28. Each graph represents the results of a limiting dilution experiment with the use of the same CD34⁺ HPC cell suspension in different conditions (ie, cytokines alone, cytokines and HDC, cytokines and stroma, cytokines and HDC and stroma). The total height of each bar represents 24 replicate wells at a given serial dilution (25 cells/well to 200 cells/well). Each well was inspected with microscopy, and cellular density was scored with a scale from 0 (no or very few cells) to 5 (densely populating the entire well). Results of a single representative donor are shown (n = 8).