Innate lymphoid cell

Innate lymphoid cells (ILCs) are a group of innate immune cells are derived from common lymphoid progenitor (CLP) and belong to the lymphoid lineage. These cells are defined by absence of antigen specific B or T cell receptor because of the lack of recombination activating gene (RAG). ILCs do not express myeloid or dendritic cell markers.

This relatively newly described group of cells has varying physiological functions; some functions are analogous to helper T cells, while the group also includes cytotoxic NK cells. Accordingly, they have an important role in protective immunity and the regulation of homeostasis and inflammation, so their dysregulation can lead to immune pathology such as allergy, bronchial asthma and autoimmune disease.

ILCs can be divided based on the cytokines that they can produce, and the transcription factors that regulate their development and function. For each newly discovered branch of the ILC family, it will be important to determine whether a cell type represents a stable lineage or just a stage of differentiation or activation. The emerging body of data about the transcription factors and cytokine signals that differentiate ILCs contributes to the evolving classification system used to identify ILCs.

In 2013 a nomenclature and classification system was proposed that divides the known ILCs into three groups.

Group 1 ILCs constitutively express transcription factor T-bet and is able to produce Th1 cytokines (notably IFNγ and TNF) after stimulation with IL-12 or IL-18.

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