A new humanised TCR transgenic mouse model to study T cells reactive to citrullinated tenascin C, a relevant...

Autoreactive T cells recognising 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 characterised transgenic mice expressing a T-cell receptor (TCR) cloned from a patient with RA and reactive with a prominent target, citrullinated tenascin C (citTNC).

A humanised TCR transgenic (hTCR-tg) mouse recognising the citrullinated tenascin C22 (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-2^b and humanised HLA-DR4 backgrounds using full-spectrum flow cytometry, cytokine enzyme-linked immunosorbent assays, and Fluorospot assays at steady state and after antigen challenge. Additionally, we investigated the presence of antibodies to citTNC and arthritis after citTNC protein immunisation.

Thymic selection of hTCR T cells differed between the 2 major histocompatibility complex class II alleles, with 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-immunised hTCR-tg mice developed arthritis after periarticular challenge with citTNC.

hTCR-tg mice expressing an RA patient-derived autoreactive TCR develop functional antigen-specific and HLA-restricted CD4⁺ T cells. The combination of humanised HLA-DR4 and TNC22 mice will be a valuable tool in the development of antigen-specific therapies translatable to human disease.