Rheumatology Unit, Department of Medicine Solna, Center for Molecular Medicine, Karolinska Institutet, Karolinska University Hospital, Stockholm, Sweden.
Rheumatology Unit, Department of Medicine Solna, Center for Molecular Medicine, Karolinska Institutet, Karolinska University Hospital, Stockholm, Sweden; Science for Life Laboratory, Department of Medicine Solna, Karolinska Institutet, Sweden; Department of Infectious Diseases, Karolinska University Hospital, Stockholm, Sweden.
J Autoimmun. 2018 Aug;92:47-56. doi: 10.1016/j.jaut.2018.04.004. Epub 2018 May 28.
ACPA-positive rheumatoid arthritis (RA) is associated with distinct HLA-DR alleles and immune responses to many citrullinated self-antigens. Herein we investigated the T cell epitope confined within α-enolase in the context of HLA-DRB104:01 and assessed the corresponding CD4 T cells in both the circulation and in the rheumatic joint. Comparative crystallographic analyses were performed for the native and citrullinated α-enolase peptides in complex with HLA-DRB104:01. HLA-tetramers assembled with either the native or citrullinated peptide were used for ex vivo and in vitro assessment of α-enolase-specific T cells in peripheral blood, synovial fluid and synovial tissue by flow cytometry. The native and modified peptides take a completely conserved structural conformation within the peptide-binding cleft of HLA-DRB1*04:01. The citrulline residue-327 was located N-terminally, protruding towards TCRs. The frequencies of T cells recognizing native eno were similar in synovial fluid and peripheral blood, while in contrast, the frequency of T cells recognizing cit-eno was significantly elevated in synovial fluid compared to peripheral blood (3.6-fold, p = 0.0150). Additionally, citrulline-specific T cells with a memory phenotype were also significantly increased (1.6-fold, p = 0.0052) in synovial fluid compared to peripheral blood. The native T cell epitope confined within α-enolase does not appear to lead to complete negative selection of cognate CD4 T cells. In RA patient samples, only T cells recognizing the citrullinated version of α-enolase were found at elevated frequencies implicating that neo-antigen formation is critical for breach of tolerance.
抗环瓜氨酸肽抗体阳性类风湿关节炎（RA）与特定的 HLA-DR 等位基因和针对许多瓜氨酸化自身抗原的免疫反应有关。在此，我们研究了在 HLA-DRB104:01 背景下局限于α-烯醇酶的 T 细胞表位，并评估了在循环和风湿关节中相应的 CD4 T 细胞。对天然和瓜氨酸化α-烯醇酶肽与 HLA-DRB104:01 复合物进行了比较晶体学分析。用天然或瓜氨酸化肽组装的 HLA 四聚体用于通过流式细胞术在体外和体外评估外周血、滑液和滑膜组织中的α-烯醇酶特异性 T 细胞。天然和修饰的肽在 HLA-DRB1*04:01 的肽结合槽内采用完全保守的结构构象。瓜氨酸残基-327 位于 N 端，朝向 TCR 突出。识别天然 eno 的 T 细胞在外周血和滑液中的频率相似，而相比之下，识别 cit-eno 的 T 细胞在外周血中的频率明显高于滑液（3.6 倍，p=0.0150）。此外，与外周血相比，具有记忆表型的瓜氨酸特异性 T 细胞也明显增加（1.6 倍，p=0.0052）。局限于α-烯醇酶的天然 T 细胞表位似乎不会导致同源 CD4 T 细胞的完全阴性选择。在 RA 患者样本中，只有识别α-烯醇酶的瓜氨酸化版本的 T 细胞以升高的频率被发现，这表明新抗原形成对于突破耐受至关重要。
