Heterogeneity in differentiation capacity among ILC precursors in human peripheral blood and tissues

Abstract

Background The origin of human Innate Lymphoid Cells (ILCs) remains less well characterised compared to mice. Single-cell RNA-sequencing recently revealed a population of ILC precursors (ILCP) expressing CD62L and CD45RA, which shows diversity in frequencies among blood, tonsil and intestine. Objective We set out to determine the differentiation capacity and epigenetic landscape of blood, tonsil and intestinal ILCP. Methods Blood, tonsil and intestinal ILCP were sort-purified on the basis of CD62L and CD45RA (CD62L+/−CD45RA+/−) and cultured on OP9-DL1 stromal cells under specific cytokine conditions. Additionally, genome-wide chromatin accessibility was measured using ATAC-sequencing. Results We show that all ILCP subsets in blood and tonsil were able to differentiate to IFN-γ-producing ILC1/NK cells. Whereas all blood ILCP subsets readily differentiated to IL-13-producing ILC2, no or very few ILC2 were generated from tonsil ILCP. In contrast, tonsil ILCP subsets showed higher ability to generate IL-22-producing ILC3, compared to blood ILCP. These data indicate that ILCP in blood are poised towards ILC1/ILC2 while ILCP in tonsil favours ILC1/ILC3 differentiation. To further dissect their development, we are currently analysing global epigenetic information of tonsil ILCP, aiming to delineate their chromatin landscape. Finally, we investigated the ILCP in intestinal samples and detected accumulation of CD62L−CD45RA+ ILCP in the inflamed mucosa of patients with inflammatory bowel disease (IBD) as compared to the non-inflamed tissue. We are currently analysing the potency of those cells. Conclusion Heterogeneity in ILC differentiation in blood and tissues could further reveal novel targets for IBD treatment.