Department of Microbiology and Immunology, The University of Western Ontario, London, ON, Canada.
Department of Microbiology and Immunology, The University of Western Ontario, London, ON, Canada; Department of Medicine/Rheumatology, The University of Western Ontario, London, ON, Canada.
J Autoimmun. 2018 May;89:75-81. doi: 10.1016/j.jaut.2017.12.002. Epub 2017 Dec 11.
Antibodies to proteins/peptides containing citrulline are hallmarks of Rheumatoid Arthritis (RA). These antibodies are strongly associated with the expression of the Shared Epitope (SE). RA patients also generate antibodies to homocitrulline-containing proteins/peptides (also referred to as anti-carbamylated protein antibodies (Anti-CarP)). This study was undertaken to investigate the relationship between homocitrulline and citrulline immune responses using an established mouse model of RA: DR4-transgenic (DR4tg) mice that express the human SE. C57BL/6 (B6) and DR4tg (on a B6 background) mice were immunized subcutaneously with a homocitrullinated peptide (HomoCitJED). Splenic T cell proliferation was evaluated by H-thymidine incorporation assay. Antibodies to homocitrullinated and citrullinated antigens were screened by enzyme-linked immunosorbent assay (ELISA). Antibody cross-reactivity was examined by inhibition with HomoCitJED and its citrullinated counterpart peptide, CitJED (the number of homocitrullines in HomoCitJED is equal to the number of citrullines in CitJED). HomoCitJED-immunized DR4tg mice developed early T and B cell responses to HomoCitJED and late responses to CitJED. These mice also developed anti-CCP2 antibodies. In some mice, antibodies to HomoCitJED were also reactive to CitJED. B6 mice immunized with HomoCitJED developed late T and B cell responses to HomoCitJED, but did not generate responses to citrullinated antigens. Unlike DR4tg mice, anti-HomoCitJED antibodies from B6 mice did not react to CitJED. In conclusion, DR4tg mice immunized with HomoCitJED developed immune responses to CitJED, indicating cross-reactivity. CitJED immune responses were dependent on the SE. HomoCitJED responses occurred in the absence of the SE (B6 mice); however, they developed earlier in DR4tg SE-expressing mice.
抗瓜氨酸化蛋白/肽抗体是类风湿关节炎 (RA) 的标志性特征。这些抗体与共享表位 (SE) 的表达密切相关。RA 患者还会产生针对含同型瓜氨酸蛋白/肽的抗体（也称为抗氨甲酰化蛋白抗体 (Anti-CarP)）。本研究旨在使用已建立的 RA 小鼠模型：表达人类 SE 的 DR4 转基因 (DR4tg) 小鼠，来研究同型瓜氨酸和瓜氨酸免疫反应之间的关系。C57BL/6 (B6) 和 DR4tg (在 B6 背景下) 小鼠通过皮下注射同型瓜氨酸化肽 (HomoCitJED) 进行免疫。通过 H-胸苷掺入测定评估脾 T 细胞增殖。通过酶联免疫吸附试验 (ELISA) 筛选针对同型瓜氨酸化和瓜氨酸化抗原的抗体。通过用 HomoCitJED 及其瓜氨酸化对应物肽 CitJED 进行抑制来检查抗体的交叉反应性 (HomoCitJED 中的同型瓜氨酸数量等于 CitJED 中的瓜氨酸数量)。HomoCitJED 免疫的 DR4tg 小鼠对 HomoCitJED 早期和晚期产生 T 和 B 细胞反应，并对 CitJED 产生晚期反应。这些小鼠还产生了抗 CCP2 抗体。在一些小鼠中，针对 HomoCitJED 的抗体也对 CitJED 有反应。用 HomoCitJED 免疫的 B6 小鼠对 HomoCitJED 晚期产生 T 和 B 细胞反应，但对瓜氨酸化抗原没有反应。与 DR4tg 小鼠不同，来自 B6 小鼠的抗 HomoCitJED 抗体对 CitJED 没有反应。总之，用 HomoCitJED 免疫的 DR4tg 小鼠对 CitJED 产生了免疫反应，表明存在交叉反应性。CitJED 免疫反应依赖于 SE。在缺乏 SE 的情况下 (B6 小鼠) 会发生 HomoCitJED 反应；然而，在表达 SE 的 DR4tg 小鼠中，它们更早出现。
