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A1337 - c-Kit Is a Marker of Distinct Type 2 Innate Lymphoid Cell (ILC2) Subpopulations with Differential Functional Properties
Author Block: T. Hochdorfer1, C. Winkler1, J. Mjosberg2, K. Pardali1; 1iMED RIA, AstraZeneca, Gothenburg, Sweden, 2Center for Infectious Medicine, Department of Medicine, Karolinska Institutet, Stockholm, Sweden.
Human ILC2 are defined by lack of a variety of lineage markers and expression of CD127, CD161, CRTH2 and variable amounts of the stem cell factor (SCF) receptor c-Kit. Previous studies have shown differential expression of c-Kit on the cell surface of ILC2 depending on the tissue of origin. However, the influence of c-Kit expression on ILC2 function has so far not been addressed. In this study we isolated ILC2 from human peripheral blood. We FACS-sorted the cells as either c-Kitlow or c-Kithigh and investigated their characteristics, including the response to co-stimulation with SCF. We found stronger GATA-3 expression in c-Kitlow ILC2 and higher CCR6 expression on c-Kithigh ILC2, implying differences in transcriptional programs and functions of the two subpopulations. The c-Kit phenotype stayed stable in short-term cultures, with both subpopulations keeping their respective c-Kit expression. In short-term stimulations we found that c-Kitlow ILC2 produced higher levels of IL-5 and IL-13 than c-Kithigh ILC2. For both subpopulations, co-stimulation with SCF augmented cytokine production even further. SCF co-stimulation also lead to production of IFN-γ, particularly in c-Kitlow ILC2. Following long-term stimulation on OP9-feeder cells we found that c-Kitlow ILC2 proliferated more than c-Kithigh ILC2. Even though the total cytokine production was higher in c-Kitlow ILC2, c-Kithigh ILC2 produced more cytokines than c-Kitlow ILC2 on a per cell basis. In the long-term stimulation, c-Kithigh ILC2 lost c-Kit expression and became phenotypically similar to c-Kitlow ILC2. Subsequently the two subpopulations produced similar amounts of cytokines at the end of the long-term culture protocol. Intracellular GATA-3 increased with stimulation and converged over the course of the long-term culture between c-Kitlow and c-Kithigh ILC2 so that both subpopulations ended up with comparable expression of the transcription factor. We are currently dissecting the temporal dynamics of c-Kit expression and ILC2 functionality in short- and long-term cultures of ILC2 and the influences of c-Kit inhibition. Given the therapeutic potential of c-Kit, we believe that our investigations might provide a novel avenue for treatment of allergic and asthmatic inflammation and give new insights on how c-Kit expression and activity influences ILC2 functions, such as proliferation, activation and plasticity.