Caveolin-1 restrains pathogenic T follicular helper cell response in primary Sjögren’s syndrome

Abstract

T follicular helper (Tfh) cells play a central role in humoral autoimmunity, including primary Sjögren’s syndrome (pSS). However, targeting Tfh cells is challenging in clinical management. Previous studies suggested that inducible T­cell co­stimulator (ICOS) directed Tfh cell motility in engaging bystander B cells, which promoted plasma cell differentiation and antibodies production. Here, we identified a novel function of caveolin-1 (Cav-1) in restraining ICOS expression in Tfh cells and pSS pathogenesis. Cav-1 deficiency significantly promoted human and murine Tfh cell responses, while Cav-1-/- mice exhibited exacerbated disease pathology of experimental SS (ESS). Peroxisome proliferator-activated receptor alpha (PPARa), a downstream transcription factor of Cav-1, rapidly repressed Icos transcription upon Tfh polarization, interestingly, independence of lipid metabolism. Phenotypic analyses suggested that Cav-1 and PPARa expressions were decreased in CD4+ T cells from pSS patients and ESS mice. Notably, pharmaceutical activation of PPARa with fenofibrate could suppress human and murine Tfh cells both in vitro and in vivo, while oral administration of fenofibrate effectively ameliorated ESS pathology in mice with acute or chronic inflammation. These results revealed an unrecognized role of Cav-1/PPARa axis in Tfh cell tolerance and pSS pathogenesis, suggesting PPARa as a promising target in the treatment of humoral autoimmunity.