Analysis of heart-infiltrating T-cell clonotypes in experimental autoimmune myocarditis in rats

Experimental autoimmune myocarditis (EAM) resembles the lethal giant cell myocarditis seen in humans, and the recurrent forms lead to dilated cardiomyopathy (DCM). EAM in rats induced by a subcutaneous injection of cardiac myosin has been shown to be a T cell-mediated autoimmune disease. alpha beta T cells have proved to be important by the observation that antibodies to alpha beta T-cell receptor (TCR) prevent disease progression. alpha beta T cells recognize antigenic peptides bound to major histocompatibility (MHC) molecules by alpha beta TCR, and complementarity determining region 3 (CDR3) is considered the most important region for antigen recognition. To elucidate the nature of this T cell-mediated myocarditis, we analyzed TCR V beta chains of heart-infiltrating T cells. In the early stage of EAM, none of 22 TCR V beta chain transcripts seemed to be dominant by reverse transcription-polymerase chain reaction analysis of total RNA and flow cytometric analysis. On the other hand, single-strand conformation polymorphism analysis of TCR V beta 8.2, V beta 8.5, V beta 10, and V beta 16 cDNA amplified by polymerase chain reaction encompassing the CDR3 revealed oligoclonal expansion in heart-infiltrating T cells isolated from animals at various disease stages. cDNA encoding V beta CDR3 from heart-infiltrating and pericardial effusion T cells in rats with EAM revealed more restricted sequences than did cells from rats with normal spleens. Clones from distinct lesions of the same animal were identical, and clones from heart-infiltrating and pericardial effusion T cells from the same animal showed overlap. Thus, CDR3 of the TCR beta chain may be important in rat EAM, and heart-infiltrating T cells are considered to recognize the specific antigen.