High dimensional analysis reveals distinct NK cell subsets but conserved response to stimulation in umbilical cord blood and adult peripheral blood

Abstract

Growing interest surrounds adoptive cellular therapies utilizing Natural Killer (NK) cells, which can be obtained from various sources, including umbilical cord blood (UCB) and adult peripheral blood (APB). Understanding NK cell receptor expression and diversity in such cellular sources will guide future therapeutic designs. We used a 20-color flow cytometry panel to compare unstimulated and cytokine-activated UCB and APB NK cells. Our analysis showed that UCB NK cells express slightly higher levels of the immune checkpoints PD-1, TIGIT, and CD96 compared to their APB counterparts. Unsupervised hierarchical clustering and dimensionality reduction analyses revealed enrichment in CD56^neg as well as mature NKp46^neg and CD56⁺ CD16⁺ NK cell populations in UCB whereas CD57⁺ terminally differentiated NK cells with variable expression of KIRs and CD16 were found in APB. These populations were conserved following stimulation with IL-12, IL-15, and IL-18. Cytokine stimulation was associated with the downregulation of TIGIT and CD16 on multiple NK cell subsets in UCB and APB. Among UCB CD16^- NK cell populations, TIGIT⁺ NK cells produced more IFN-γ than their TIGIT^- counterparts. Our data demonstrate higher immune checkpoint expression on UCB NK cells compared to APB. However, the expression of TIGIT immune checkpoint is not indicative of NK cell exhaustion.

Keywords: Natural Killer cells; flow cytometry; umbilical cord blood.