A new humanized TCR transgenic mouse model to study citrullinated tenascin C reactive T cells relevant to rheumatoid arthritis

ObjectivesAutoreactive T cells recognizing citrullinated antigens, although rare and difficult to study, are implicated in rheumatoid arthritis (RA). To allow functional studies and manipulation of such T cells, we have generated and characterized transgenic mice expressing a TCR cloned from an RA patient and reactive with a prominent target, citrullinated tenascin C (citTNC). MethodsA humanized TCR transgenic (hTCR-tg) mouse recognizing the citrullinated TNC22 (citTNC22) antigen in an HLA-DRB1*04:01 (HLA-DR4) restricted manner was developed by genetically engineering a chimeric TCR expressing murine constant domains and human V(D)J sequences. hTCR-tg mice were immune phenotyped in murine H-2b and humanized HLA-DR4 backgrounds using full spectrum flow cytometry, cytokine ELISAs and fluorospot assays at steady-state and after antigen challenge. Additionally, we investigated the presence of antibodies to citTNC and arthritis following citTNC protein immunization. ResultsThymic selection of hTCR T cells differed between the two MHC-II alleles, with a normal CD4+ T cell development observed solely under HLA-DR4 restriction. The chimeric hTCR maintained its citTNC22 specificity in vitro and ex vivo, without cross-reactivity to native TNC22 or other citrullinated autoantigens. hTCR-tg CD4+ T cells responded to antigen challenge in vivo and provided support to IgG class-switch and antigen-specific antibody production. Moreover, protein immunized hTCR-tg mice developed arthritis after periarticular challenge with citTNC. ConclusionshTCR-tg mice expressing an RA patient-derived autoreactive TCR develop functional antigen-specific and HLA-restricted CD4+ T cells. The combination of humanized HLA-DR4 and TNC22 mice will be a valuable tool in the development of antigen-specific therapies translatable to human disease.