Background: Viral infection and anti-cardiac immunity are involved in the pathogenesis of dilated cardiomyopathy (DCM). Immunity targeting particular antigens may evoke expansion of reactive T-cell clones.
Material and methods: Myocardial tissues from explanted hearts were investigated for clonal T-cell-receptor- (TCR-) ß rearrangements by an established semi-nested polymerase chain reaction (PCR), followed by high-resolution GeneScan analysis and direct sequencing. From 17 explanted DCM hearts, 3 myocardial samples each were obtained from the right ventricle, the septum, and the left ventricle (total: 9 myocardial samples per case). Six explanted hearts with non-DCM cardiomyopathy entities served as controls.
Results: GeneScan analysis revealed polyclonal TCR-ß rearrangements in all controls. In contrast, at least 1 myocardial sample in 9 out of 17 DCM hearts (total: 20 of the 81 DCM specimens) displayed single dominant TCR-ß PCR products consistent with the presence of clonal T-cell populations. Direct sequencing of the clonal TCR-ß PCR-products disclosed an involvement of Vß 19.01 segments in 14 of the dominant amplificates (70%). Further TCR-Vß segments involved in clonal TCR-ß rearrangements of DCM hearts were Vß 6-1.01 (n=1), Vß 6-3.01 (n=2), Vß 6-5.01 (n=1), Vß 10-3.02 (n=1), and Vß 19.03 (n=1).
Conclusions: The detectability of clonal TCR-ß rearrangements indicates a pathogenic relevance of this finding in DCM. The predominance of Vß 19.01 segments suggests that the immune response in DCM patients targets particular epitopes. However, the partly heterogenic TCR-ß populations in various myocardial samples from the respective cases support the notion that T-cell immunity may target multiple epitopes in human DCM.