Figure 6.
IL-15 drives CB-NKimsubset diversity and functional maturation. (A) Frequency of CB-NKim subset within the total NK cell population in CB units before infusion (left) compared with adult healthy PB donors (right). Boxes represent median with minimum to maximum range. ****P ≤ .0001. (B) Schema of CB NK cell in vitro experiments. CB-NKim (NKG2A+CD57−CD16−NKG2C−CD62L+) and CB-NK mature (CD16+CD62L−) were sort-purified and cultured in the presence of IL-2 (10 units/mL) or IL-15 (20 ng/mL) for 7 days. Representative flow plots show enhanced IFN-γ and TNF-α response to K562 targets by CB-NKim cells and mature CB-NK cells cultured for 7 days in the presence of IL-2 or IL-15. Inset numbers are the percentages of IFN-γ- and TNF-α-positive NK cells within the indicated gated regions. (C) Heat map shows expression of transcription factors and cytotoxicity markers in CB-NKim (NKG2A+CD57−CD16−NKG2C−CD62L+) and CB-NK mature (CD16+CD62L−) before and after culture with IL-2 (10 units/mL) or IL-15 (20 ng/mL) for 7 days and in PB samples collected from patients at day 100 after CBT. Each column represents 1 donor and each row reflects expression of a certain maker for each annotation, highlighting their distinct expression in immature subset and mature subset. Color scale shows the expression level of each marker, with red representing higher expression and blue lower expression. (D) Stacked bar graphs showing the comparison of frequency of CB-NKim subset before stimulation (baseline) or after stimulation with IL-2 (10 units/mL) or IL-15 (20 ng/mL) for 7 days. *P ≤ .01. The y-axis represents the proportion of CB-NKim vs mature NK cells after ex vivo culture of purified CB-NK cells with different cytokines. (E) Box plots showing diversity of CB-NKim subset before stimulation (baseline) or after stimulation with IL-2 (10 units/mL) or IL-15 (20 ng/mL) for 7 days. *P ≤ .01. (F) Box plots showing the IL-15 concentration in plasma samples collected from patients with CMV reactivation post-CBT (n = 19; median, 27.2 pg/ml; range, 16.3-44.9 pg/mL) vs those who did not (n = 24; median, 15.6 pg/mL; range, 13.5-31.9 pg/mL) in the first 100 days after CBT. ****P ≤ .0001.