Human CD127 negative ILC2s show immunological memory.

Group 2 Innate Lymphoid Cells (ILC2s) are key players in type 2 immunity and contribute to maintaining homeostasis and responding to inflammation. ILC2s are implicated in the development of type 2 inflammation-mediated chronic disorders like asthma. While memory ILC2s have been identified in mouse, it is unknown whether human ILC2s can acquire immunological memory. Here, we demonstrate the persistence of CD45RO, a marker previously linked to inflammatory ILC2s, in resting ILC2s that have undergone prior activation. A high proportion of these cells concurrently reduce the expression of the canonical ILC marker CD127 in a tissue specific manner. Through isolation and in vitro stimulation of CD127- CD45RO+ ILC2s, we observed an augmented ability to proliferate and produce cytokines. CD127- CD45RO+ ILC2s are found in both healthy and inflamed tissues and display a gene signature of cell activation. Our findings suggest that human ILC2s can acquire innate immune memory and warrants a revision of the current strategies to identify human ILC2s. Single cell sequencing of human dermal CD45+ Lin- cells