IL-36 family cytokines induce immune activation in primary Sjogren's disease

Primary Sjogren's disease (pSD) is a chronic autoimmune disease. Patients often experience dry eyes and mouth in addition to extra-glandular manifestations. In pSD, underlying disease mechanisms remain poorly understood and no curative therapies are available. Myd88 is a cytosolic adapter molecule that is utilized by both innate and adaptive immunity. While Myd88 is required for pSD pathogenesis, the mediators of Myd88 activation are not well understood in this disease. IL-36 family cytokines (IL-36a, IL-36b, and IL-36g) rely on Myd88 for signaling. These cytokines mediate inflammation in other autoimmune diseases, but the role of these cytokines in pSD is unknown. Our objective was to investigate the role of IL-36 cytokines in pSD using a mouse model and patient samples. We isolated spleens from pSD mice and healthy controls. Splenocytes were cultured overnight in media alone, or media containing IL-36α, IL-36β, or IL36γ. Cells and supernatants were harvested and flow cytometry, ELISAs, and cytokine multiplex arrays were performed. In addition, we performed ELISAs on sera from pSD patients and controls to quantify levels of IL-36α, IL-36β, and IL36γ. Our results revealed that IL-36 family cytokines induced elevated expression of the activation markers CD69 and CD86 in B cells from pSD mice as compared to those from controls. Moreover, the pro-inflammatory cytokines IFNγ, IL-1α, IL-1β, IL-6, IL-12 p70 and GM-CSF were increased in pSD splenocyte cultures following stimulation with IL-36 family cytokines as compared to those from controls. Finally, sera from pSD patients displayed elevated levels of IL-36α and IL36γ as compared to non-pSD controls. In conclusion, our study shows that IL-36 family cytokines can induce heightened immune activation in the context of pSD and pSD patients have elevated levels of IL-36 family cytokines in sera. Thus, targeting of IL-36 signaling networks may represent a novel therapeutic strategy for patients with pSD.