Dysregulated IL-23/IL-17 responses have been linked to psoriatic arthritis and other forms of spondyloarthritides (SpA). RORγt, the key Thelper17 (Th17) cell transcriptional regulator, is also expressed by subsets of innate-like T cells, including invariant natural killer T (iNKT) and γδ-T cells, but their contribution to SpA is still unclear. Here we describe the presence of particular RORγt+T-betloPLZF− iNKT and γδ-hi T cell subsets in healthy peripheral blood. RORγt+ iNKT and γδ-hi T cells show IL-23 mediated Th17-like immune responses and were clearly enriched within inflamed joints of SpA patients where they act as major IL-17 secretors. SpA derived iNKT and γδ-T cells showed unique and Th17-skewed phenotype and gene expression profiles. Strikingly, RORγt inhibition blocked γδ17 and iNKT17 cell function while selectively sparing IL-22+ subsets. Overall, our findings highlight a unique diversity of human RORγt+ T cells and underscore the potential of RORγt antagonism to modulate aberrant type 17 responses.

Our data reveal an important and novel interplay between myeloid cells and tissue resident cells at entheseal sites that is regulated by A20. In the absence of A20, STAT1 but not STAT3 expression is enhanced leading to STAT1-dependent inflammation. Therefore, A20 acts as a novel endogenous regulator of STAT1 that prevents onset of enthesitis.

ObjectiveTransforming growth factor β superfamily members are involved in the pathogenesis of systemic sclerosis (SSc). Growth differentiation factor 15 (GDF‐15) is a distant member of this family. We undertook this study to evaluate the role of GDF‐15 in SSc pathogenesis.MethodsA longitudinal prospective cohort of SSc patients was screened for serum GDF‐15 levels using enzyme‐linked immunosorbent assay, and associations with clinical data were analyzed. In vitro stimulation experiments were performed on lung fibroblasts. The role of GDF‐15 in fibrosis development in vivo was evaluated in the bleomycin lung fibrosis model in GDF‐15–deficient mice.ResultsGDF‐15 was measured at baseline in serum samples from 119 SSc patients. An increase in GDF‐15 levels was observed in patients classified as having no skin involvement, those with limited cutaneous SSc, and those with diffuse cutaneous SSc. Moreover, baseline serum GDF‐15 levels correlated strongly with disease activity and extent of organ involvement, particularly clinical symptoms of lung fibrosis, including impact on lung function at prospective followup. This was mimicked in the bleomycin model of SSc, in which animals exposed to bleomycin had elevated expression levels of GDF‐15 in lung tissue. Lung fibroblasts isolated from GDF‐15–deficient mice showed reduced induction of interleukin‐6 and CCL2 upon bleomycin stimulation. Surprisingly, no differences in fibrosis development were observed between wild‐type and GDF‐15–deficient animals.ConclusionAn intriguing profile of serum GDF‐15 levels was found in SSc patients. GDF‐15 expression is induced during fibrosis development and markedly correlates with lung function impairment in this disease. The protein may participate in fibrosis initiation, but is not indispensable in the course of fibrosis development in vivo.