Tissue-resident memory-like ILCs: innate counterparts of TRM cells

摘要

Innate lymphoid cells (ILCs), including natural killer (NK) cells, ILC1s, ILC2s, ILC3s, and lymphoid tissue-inducer (LTi) cells, are a group of innate lymphocytes that confer early defense against pathogenic infections and tumor development (Cella et al., ; Cupedo et al., ; Sanos et al., ; Satoh-Takayama et al., ; Moro et al., ; Neill et al., ; Fuchs et al., ; Klose et al., ; Vivier et al., ). However, recent studies have uncovered the adaptive features of NK cells and other ILCs (O’Leary et al., ; Cooper et al., ; Sun et al., ; Peng et al., ; Martinez-Gonzalez et al., ; Wang et al., , ). Mouse cytomegalovirus (MCMV) infection induces the generation of memory Ly49H NK cells (Sun et al., ), and cytokine stimulation with interleukin (IL)-12/15/18 mediates memory-like NK cell formation (Cooper et al., ). MCMV- and cytokine-induced memory NK cells circulate in the blood and populate throughout the body. Herein, we refer to these cells as conventional memory NK cells (Table  ). Besides this type of memory NK cells, recently defined memory ILCs show long-term residency in peripheral tissue, but not in the circulation, and they are referred to as tissue-resident memory ILCs (Table  ). For example, hapten-induced memory NK cells and ILC1s are liver-resident (Paust et al., ; Peng et al., ; Li et al., ; Wang et al., ), and IL-33-responsive ILC2s can acquire memory potential and persist in the lung (Martinez-Gonzalez et al., ). These new findings prompt us to re-examine the biology of ILCs and their roles in disease progression.