Single-cell analysis of the dLN-tumor OL clones following anti-CD4 mAb treatment

The repertoire of tumor-infiltrating T cells is a novel perspective to characterize effective anti-tumor T cell responses. Previous studies reported that the oligoclonal expansion in tumor T-cell repertoire is associated with anti-tumor effects. However, the contribution of the expansion of diverse T-cell clones remained unclear. We demonstrated that the polyclonal fraction of tumor-reactive T-cell repertoire consisting of relatively minor clones, increased in tumor-bearing mice treated with anti-PD-L1 or anti-CD4 monoclonal antibodies (mAbs), while the oligoclonal fraction consisting of major clones was unchanged. Moreover, the polyclonal fraction was enriched with progenitor exhausted T cells, essential for a durable anti-tumor response, and more dependent on CCR7+ migratory dendritic cells, responsible for priming tumor-reactive T cells in the tumor-draining lymph node (dLN). These results proposed that the expansion of diverse tumor-reactive clones, “clonal spreading,” is an important mechanism by which anti-PD-L1 and anti-CD4 treatments exert robust and durable anti-tumor T-cell responses. CD8+ TILs and CD8+ CD44high T cells in dLN were collected from a B16F10 tumor-bearing mouse treated with anti-CD4 mAb. Single-cell targeted RNA sequencing combined with TCR sequencing (scRNA/TCRseq) was perfomed on CD8+ TILs. Bulk TCR sequencing was performed on dLN CD8+ CD44high T cells. T cell clones that overlap between tumor and dLN were identified.