| Abstract: | Objective Antibodies toward the citrullinated form of the synovial antigen vimentin are specific for rheumatoid arthritis (RA) and are associated with HLA–DRB1*0401. This suggests that T cells specific for peptides derived from citrullinated vimentin presented in the context of HLA–DRB1*0401 may contribute to the etiopathogenesis of RA. The aim of this study was to identify immunodominant epitopes from citrullinated vimentin presented by HLA–DRB1*0401 and to characterize the resulting T cell responses. Methods We first predicted an HLA‐binding T cell epitope from citrullinated vimentin based on the binding motif of HLA–DRB1*0401 and then confirmed its affinity. A class II major histocompatibility complex (MHC) tetramer loaded with the citrullinated form of vimentin aa 59–78 (cit‐vimentin aa 59–78) was constructed and used to screen for specific T cells in HLA–DRB1*0401–transgenic mice, patients with RA, and healthy control subjects. Additionally, the cytokine output following cit‐vimentin aa 59–78 challenge was analyzed in patients and healthy control subjects by multicolor flow cytometry and Luminex‐based analysis. Results The citrullinated form of vimentin aa 59–78 bound to HLA–DRB1*0401, but the native form could not. Subsequently, cit‐vimentin aa 59–78–specific T cells were detected in immunized mice and in the periphery of both HLA–DR*0401–positive healthy control subjects and HLA–DR*0401–positive patients with RA, using class II MHC tetramers, CD154 up‐regulation, and intracellular cytokine measurements. As demonstrated in cell culture supernatants, the production of cytokines (predominantly interferon‐γ) in response to cit‐vimentin aa 59–78 was significantly higher in patients compared with controls. Conclusion Here, we describe a posttranslational modification of an RA candidate autoantigen toward which HLA–DRB1*0401–restricted T cells can be detected in both patients with RA and healthy controls but for which a proinflammatory response is observed uniquely in patients with RA. |
