Background/Purpose: Behçet disease (BD) is an inflammatory chronic disease characterized by alternation of active and inactive phases. Steroids, Colchine, Azathioprine (Aza) and interferon α are commonly used for BD management [Hatemi G. Ann Rheum Dis 2018]. NKG2D is a receptor expressed by NK, NKT and CD8 T cells that acts as a sensor for self antigens induced by infections, stress and neoplastic transformation [Lanier LL. Cancer Immunol Res 2015]. We have demonstrated that BD patients are characterized by higher NKG2D^pos NK, NKT and T cells [Bonacini M. Front Immunol 2018]. We hypothesized that following NKG2D increase, BD patients are more prone to respond to NKG2D ligands, which could lead to cyclic auto-inflammation. Drugs able to inhibit NKG2D expression might thus be the most promising in BD patients. The aims of the present work were to: 1) evaluate the effects in vitro on NKG2D expression by immune cells of drugs used for BD management, epigenetic drugs and nutraceuticals; 2) determine if the effects differed between BD patients and controls (CTR); 3) analyse circulating levels of NKG2D ligands.

Methods: Peripheral Blood Mononuclear Cells (PBMCs) from 5 active BD patients naive from therapy and 5 CTR were treated for 48h with 500 ng/ml Dexamethasone (Dexa) or 3000U interferon α-2A or 1µM Colchicine or 30µM Aza or 250µM iBet-762 or 730µM Valproic Acid or 5µM Curcumin. NK (CD56^posCD3^neg), NKT (CD56^posCD3^pos), CD8 T (CD56^negCD3^posCD8^pos) cell percentages and NKG2D levels on their surface were evaluated by flow cytometry. To mimic the active phase of the disease, PBMCs were treated with IL-15 for 24h followed by drugs treatment for additional 48h in presence of IL-15. The same analyses were performed. The levels of NKG2D soluble ligands were quantified in plasma of 11 active BD patients naive from therapy and 22 CTR. For 7 BD patients,plasma during the active and inactive phases were analysed.

Results: Unstimulated PBMCs from BD patients cultured with Dexa showed a reduction in NK cell percentages. Conversely, Dexa increased NK cells percentages in activated PBMCs. All the treatments reduced NKG2D expression on NK, NKT and CD8 T cells, with the exception of interferon α-2A treatment that did not modify NKG2D levels on unstimulated PBMCs. Similar effects were observed after treatment of PBMCs from BD and CTR. Higher concentrations of soluble MICA, one of the ligands of NKG2D, were observed in plasma from active BD patients than CTR. MICA levels decreased in BD patients who progressed from active to inactive phase.

Conclusion: BD patients were characterized by higher soluble MICA that increases the possibility of immune cell activation. Drugs commonly used for BD management were able to down-regulate NKG2D levels on immune cells surface, reducing their activation capacity. In addition drugs used for the treatment of other diseases, such as Valproic Acid used for breast cancer and iBet-762 used for pancreatic cancer, showed the same effects on NKG2D expression. The reduction of NKG2D expression on immune cells induced by the drugs was independent of the BD condition. This should be considered when treating patients in whom it is important to maintain the immune surveillance, such as cancer patients.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/modulation-of-nkg2d-expression-on-nk-nkt-and-cd8-t-lymphocytes-by-in-vitro-treatments-of-immune-cells-from-patients-with-behcet-disease/