Characterisation of Intestinal Innate Lymphoid Cells

Innate Lymphoid Cells (ILCs) derive from a lymphoid progenitor. They are divided into three groups based on the transcription factors and cytokines they express: ILC1, ILC2 and ILC3. We have recently shown that intestinal ILCs traffic to mesenteric lymph nodes (MLNs) where they populate the interfollicular area.

To investigate the properties of migratory ILCs, we isolated cells from the small intestine (SI), colon and MLNs of C57BL/6 mice. ILC subsets were identified by staining for T-bet, GATA-3 and Roryt, and their proliferative capacity was assessed. ILC2s comprise the main population of ILCs in the colon (4,5% of CD45+ cells), whereas the SI contains mainly ILC2s and ILC3s. Strikingly, a population of Roryt and T-bet co-expressing ILCs is increased in the SI. However all three ILC populations are found at similar frequencies in the SI and colon-draining regions of the MLNs. Furthermore, the proliferative capacity of ILCs differs greatly between the ILC subsets and tissues; the ILC1 population in the MLNs is highly proliferative compared to ILC3s in the gut and MLNs. These data indicate that different mechanisms maintain steady state intestinal ILC populations. Future investigations will aim to uncover the functions of the migratory ILCs in the intestine.