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Background Cell metabolism, in addition to providing energy and biochemical building blocks, also regulates immune cell function. We have increased our understanding of how natural killer cells (NK cell) metabolism impacts human NK cell function; however, little is known about NK cell role and metabolic changes in autoimmune diseases. The dysfunctional NK cell phenotype observed in pathological settings linked to defective cell metabolism will give insights into the development of new therapies for inflammatory diseases. IBD is an autoimmune disease of unknown origin characterised by severe gut inflammation and increased risk of colorectal cancer. NK cells can augment autoimmune responses through their activation of adaptive immune response by interaction with macrophages, dendritic cells and T cells; therefore, it is essential to decipher NK cells function in IBD to propose novel therapeutic targets. In this study, we defined the phenotype and metabolic profile of NK cells isolated from peripheral blood of IBD patients. Methods Blood samples were obtained from healthy donors and IBD patients from whom written consent had been obtained. PBMC were isolated by Lymphoprep (Axis-Shield) gradient. PBMC were stained with a combination of cell surface receptors, intracellular cytokines, proteins and analysed by flow cytometry. Cells were either stained ex vivo or after overnight stimulation with cytokine combination IL-12 + IL-15 and in the presence or absence of mTORC1 inhibitor rapamycin. Changes in OxPhos or glycolysis were detected by XFp extracellular ux analyser (Agilent Technologies). Mitochondria mass and polarisation were measured by flow cytometry utilising MitoTracker Green and MitoTracker Red, respectively (ThermoFisher). Results NK cells from IBD patients have impaired mTORC1 activity (a key signalling pathway regulating cell metabolism), which is associated with increased expression of pro-inflammatory cytokines IL-17 and TNF-α. Patients NK cells have dysfunctional mitochondria characterised by reduced mitochondria mass, low membrane potential and limited OXPHOS and glycolysis. Furthermore, patients NK cells have limited IFNγ production, reduced TRAIL expression and defective capability of killing cancer cells. Conclusion Taken together, our results strongly imply that NK cells from IBD patients have a distinct bioenergetic programme that favours the increased production of pro-inflammatory cytokines. This might be an important unknown defect of NK cells in the regulation of inflammation in IBD that can be used for the development of new treatments. Further studies need to be conducted to identify the reason for the observed defects and determination of other key metabolic pathways involved in NK-cell function during IBD.

P104 Defective metabolism mediates NK cell dysfunction in inflammatory bowel disease (IBD)