Double-negative T cells ameliorate psoriasis by selectively inhibiting IL-17A-producing γδlow T cells

Background Psoriasis is a chronic immune-mediated skin condition. Although biologic treatments are effective in controlling psoriasis, some patients do not respond or lose response to these therapies. Thus, new strategies for psoriasis treatment are still urgently needed. Double-negative T cells (DNT) play a significant immunoregulatory role in autoimmune diseases. In this study, we aimed to evaluate the protective effect of DNT in psoriasis and explore the underlying mechanism. Methods We conducted a single adoptive transfer of DNT into an imiquimod (IMQ)-induced psoriasis mouse model through tail vein injection. The skin inflammation and IL-17A producing gamma delta T cells were evaluated. Results DNT administration significantly reduced the inflammatory response in mouse skin, characterized by decreased skin folds, scales, and red patches. After DNT treatment, the secretion of IL-17A by RORc(+) gamma delta(low) T cells in the skin was selectively suppressed, resulting in an amelioration of skin inflammation. Transcriptomic data suggested heightened expression of NKG2D ligands in gamma delta(low) T cells within the mouse model of psoriasis induced by IMQ. When blocking the NKG2D ligand and NKG2D (expressed by DNT) interaction, the cytotoxic efficacy of DNT against RORc(+)IL17A(+) gamma delta(low) T cells was attenuated. Using Ccr5(-/-) DNT for treatment yielded evidence that DNT migrates into inflamed skin tissue and fails to protect IMQ-induced skin lesions. Conclusions DNT could migrate to inflamed skin tissue through CCR5, selectively inhibit IL-17-producing gamma delta(low) T cells and finally ameliorate mouse psoriasis. Our study provides feasibility for using immune cell therapy for the prevention and treatment of psoriasis in the clinic.