TIGIT and neoplasm: Circulating Sepsecs-specific CD4 T cells and other circulating self-antigen-specific CD4 T cells have an exhausted phenotype (expressing PD-1, TIGIT and CTLA-4) which is a characteristic of TPH cells in damaged tissues and of tissue-resident memory (TRM)-like CD4 T cells in the tumor environment and other tissues22,24,30,38–44.