Tertiary lymphoid structures harbour stem-like tumour-specific T cells

Tertiary lymphoid structures (TLSs) are associated with improved responses to immune checkpoint blockade across solid tumours^1,2, but how they impact the phenotypic properties of tumour-specific T cells remains unclear. Here we found, across 24 treatment-naive renal cell carcinoma (RCC) tumours, that TLS-containing tumours are more heavily infiltrated by exhausted CD8⁺ T cells and have a reduced terminal exhaustion transcriptional program compared with TLS^- tumours. Specificity screening of 554 T cell clonotypes expanded within the microenvironment of 6 RCC tumours revealed 82 TCRs that were reactive against tumour cells and/or RCC antigens. A subset of tumour-specific T cell clonotypes (12%) was enriched within TLSs, and these expressed an increased program of stem-like progenitor exhaustion, associated with favourable anti-tumour immunity. However, in 60 independent RCC tumours, macrophages within tumour margins of TLS-containing tumours had an inferred immunosuppressive phenotype and were colocalized with exhausted putative tumour-reactive T cells in a subgroup that was further analysed, therefore supporting this mode of immune evasion as a counterbalance to T cell immune pressure. Our data reveal that TLSs are reservoirs of tumour-specific T cells with stem-like progenitor features that could be leveraged by T cell immunotherapies.