Phd in IINNOVATION IN IMMUNO-MEDIATED AND HEMATOLOGICAL DISORDERS

Thesis title: Deconstructing the molecular programs of Natural Killer cells to identify novel targets in intestinal inflammation

Innate lymphocytes are a heterogeneous family of immune cells that lack the specific antigen receptors typical of T and B lymphocytes, playing a crucial role as a first line of immune defence. This group includes Natural Killer (NK) cells and innate lymphoid cells (ILCs), which are further divided into ILC1, ILC2 and ILC3. ILCs are particularly abundant in the gut, where they contribute to both protective immunity and the maintenance of tissue homeostasis. NK cells are traditionally viewed as circulating lymphocytes that infiltrate tissues to exert cytotoxic effector functions, although they can also acquire tissue-resident characteristics. During inflammation, NK cells can accumulate in the intestine and contribute to the immune response through the production of IFN-γ. This project focused on characterizing NK cell subsets under both homeostatic conditions and during their expansion in gut inflammation, using the DSS-colitis model. Adoptive transfer experiments were performed to assess the presence and the persistence of tissue-resident NK cells after the resolution of inflammation. Transcriptomic analyses identified IL-10, acting upstream of STAT3, as a potential driver of tissue-resident NK cell formation in the gut. In vivo blockade of IL-10 during colitis impaired NK cell differentiation toward a tissue-resident phenotype. Furthermore, a central role for STAT3 in directing NK cells toward the tissue-resident program was demonstrated by CRISPR-Cas9 approach, moreover the conditional mouse model Ncr1ΔStat4 revealed an additional supporting contribution of STAT4 in this process. Finally, using patients with hyper-IgE syndrome (AD-HIES) carrying STAT3 loss-of-function mutations, flow cytometry analyses indicated that the IL-10/STAT3 axis in driving NK cells tissue-residency is conserved in humans. Collectively, these data underscore the importance and evolutionary conservation of the IL-10/STAT3 axis in promoting the tissue-resident phenotype of NK cells, further corroborated by analyses of AD-HIES patients. Given the critical contribution of NK cells to inflammatory diseases, these findings highlight the IL-10/STAT3 axis and tissue-resident NK cell populations as promising targets for therapeutic intervention, providing a foundation for strategies aimed at modulating NK cell function in these diseases.