Maturation of cord blood natural killer (NK) cells differs amongst neonates

106 Maturation of cord blood natural killer (NK) cells differs amongst neonates Amanda L. Prince, Levi B. Watkin, Jordan S. Orange, Kjersti M. Aagaard, Emily M. Mace Baylor College of Medicine, Houston, TX, Columbia University, TX, Columbia University, New York, NY OBJECTIVE: The source, timing of colonization, and stability of the neonatal microbiome is largely unknown. We and others have demonstrated that infant colonization may begin in utero, challenging the notion that neonates are born sterile. However, neonates are particularly vulnerable to viral infection due to dampened responses from NK cells and delayed maturation of adaptive immunity. Given the degree of variability in neonatal vulnerability to infection, we hypothesized that intrauterine exposure to microbes enables a greater diversity of NK cells in the neonates, relative to the adult, to allow for immune tolerance. Here, we performed multiparametric flow cytometry analyses to dissect the normal range and expression of human innate lymphoid cell developmental markers from umbilical cord (UC) blood. STUDY DESIGN: UC blood was collected from neonates at delivery (n1⁄450). Leukocytes were isolated using a Ficoll gradient. Isolated cells were stained with innate lymphoid cell maturation markers. Additionally, isolated cells were stimulated for 4-5 hours prior to staining for functional markers. Data was acquired by flow cytometry and analyzed using FlowJo X and Cytobank. Spanning analysis density of events (SPADE) analysis was applied to identify NK cell developmental subsets by individual. Diversity between neonates and adults was calculated using Simpson’s Diversity Index. RESULTS: Examination of innate lymphoid cell (ILC) maturation via SPADE analysis identified high inter-individual variation amongst neonates (Fig. A). When utilizing Simpson’s diversity index to examine maturation of NK cells and ILCs, we found significantly higher diversity of NK cell populations in neonates when compared to adults (p < 0.04, Fig. B). Additionally, function of NK cells varied amongst neonates when examining degranulation and cytokine markers (Fig. C). CONCLUSION: Our findings suggest diversity in stages of NK cell development between individual neonates that may reflect early immune exposure and harken viral susceptibility. Given ours and