The expanding family of innate lymphoid cells: regulators and effectors of immunity and tissue remodeling

A family of innate lymphoid cells exist that is capable of rapid cytokine production. Spits and Di Santo review the developmental relationships and physiologic function of this expanding family. Research has identified what can be considered a family of innate lymphoid cells (ILCs) that includes not only natural killer (NK) cells and lymphoid tissue–inducer (LTi) cells but also cells that produce interleukin 5 (IL-5), IL-13, IL-17 and/or IL-22. These ILC subsets are developmentally related, requiring expression of the transcriptional repressor Id2 and cytokine signals through the common γ-chain of the IL-2 receptor. The functional differentiation of ILC subsets is orchestrated by distinct transcription factors. Analogous to helper T cell subsets, these evolutionarily conserved yet distinct ILCs seem to have important roles in protective immunity, and their dysregulation can promote immune pathology.