The human CD34(−)CD117(+)CD56(−)NKp44(−) population in secondary lymphoid tissue serves as a common progenitor to NK cells and ILC2s

Abstract

Abstract The developmental pathways of human innate lymphoid cells (ILCs) have not been fully elucidated. We reported that human natural killer (NK) cells can derive from progenitor cells naturally residing in tonsils. We hypothesized that Group 2 ILCs (ILC2s) also develop in tonsils through a shared pathway. In support of this, ex vivo flow cytometry analyses of enriched human tonsil ILCs revealed a putative pathway of human CD294(+) ILC2 development stemming from a lineage (Lin)(−)CD34(−)CD117(+) population from which non-overlapping CD94(+) NK cells also emerged. Furthermore, when purified tonsil Lin(−)CD34(−)CD117(+) cells were cultured for 28 days with murine OP9 stroma expressing the human Notch ligand, Delta-like 1, in the presence of human interleukin-7 and Flt3 ligand, they produced mutually distinct and functionally mature populations of CD94(+) NK cells and CD294(+) ILC2s. The tonsil Lin(−)CD34(−)CD117(+) population is heterogeneous for CD56 and NKp44. Evaluation of the in vitro lineage differentiation potentials of subsets within the Lin(−)CD34(−)CD117(+) population according to NKp44 and CD56 revealed that NKp44(−)CD56(−) cells gave rise to both NK cells and ILC2s, whereas fractions expressing NKp44 and/or CD56 gave rise to NK cells but only to negligible ILC2s. In fact, the NKp44(−)CD56(−) population gave rise to a significantly higher percentage of ILC2s (7.50 ± 0.6) compared to the NKp44(+)CD56(+/−) populations (1.22 ± 0.4) (n = 5, p < 0.001). These data support a model whereby human NK cells and ILC2s can develop from a common Lin(−)CD34(−)CD117(+)CD56(−)NKp44(−) progenitor in tonsils and that the acquisition of NKp44 and/or CD56 restricts lineage differentiation potential towards the NK cell lineage.