[Innate Lymphoid Cells: new actors of immunity]

The world of lymphocytes has recently expanded. A new group of cells, innate lymphoid cells (ILCs) has been defined. It includes lymphoid cells that have been known for decades, such as natural killer (NK) cells, and lymphoid tissue--inducer (LTi) cells. NK cells recognize a vast array of tumor cells, which they help to eliminate through cytotoxicity and the production of cytokines, such as interferon-γ). (IFN-γ). Advances in our understanding of NK cell biology have led to a growing interest in the clinical manipulation of these cells in cancer. The other ILCs are found mostly in the mucosae and mucosal-associated lymphoid tissues, where they rapidly initiate immune responses to pathogens in the absence of specific sensitization. Here, we outline the basic features of ILCs and review the role of ILCs other than NK cells in cancer. Much of the role of ILCs in cancer remains unknown, but several findings should lead to further efforts to dissect the contribution of different ILC subsets to the promotion, maintenance, or elimination of tumors at various anatomic sites. This will require the development of standardized reagents and protocols for monitoring the presence and function of ILCs in human blood and tissue samples.