Profiling site specific TCR diversity of CD4+ T Cells in mice undergoing cardiac dysfunction

Purpose: Despite the well-established association between T cell-mediated inflammation and non-ischemic heart failure (HF), the specific mechanisms triggering T cell activation during the progression of HF and the antigens involved are poorly understood. We hypothesized that clonal expansion of CD4+ T cell in response to cardiac neoantigens promote the progression of HF. Methods: We used transverse aortic constriction (TAC) in mice to trigger HF and profiled the TCR repertoire by mRNA sequencing of CD4+ T cells from 3 pooled Nur77GFP reporter mice, which transiently express GFP upon TCR engagement. We performed TCR clonal analysis of 5000 TCR-activated GFP+CD4+ T cells sorted from the LV, and 5000 CD4+ T cells sorted from the thymus, the inguinal lymph nodes (iLNs) and the heart-draining mediastinal lymph nodes (mLNs) by bulk RNA sequencing of the TCR beta chain after 8wks of TAC surgery. Paired-end 300 base pair reads were obtained by Illumina sequencing and aligned and assembled using MiXCR software. Results: As expected, the greatest number of unique TCR beta clonotypes (4412 clones) – and therefore the highest TCR diversity – was identified in the thymus. The heart draining mLNs showed a much lower degree of TCR clonal diversity relative to the peripheral iLNs, suggesting that cardiac antigen-driven clonal expansion occurs at the mLNs that directly drain the heart. TCR-activated GFP+CD4+ T cells in the LV represented even lower TCR diversity relative to other sites. Conclusion: Collectively, our study demonstrates that in response to cardiac pressure overload, CD4+ T cells clonally expand in the heart-draining mLN; whilst a limited repertoire of CD4+ T cell clones engage endogenous antigens in the heart. Overall design: TCR profiling of CD4+ T cells in 3 pooled Nur77GFP reporter mice after 8 weeks of TAC surgery.