ICOS and neoplasm: In addition, some scholars sorted PD-1highCD4+CD8+ T cells by flow cytometry for single-cell sequencing, found the presence of 11 clustered CD4/CD8 double positive T cell (DPT) subpopulations with different cytotoxicity, depletion and activation scores, and which were enriched in the tumor marginal zone; The above DPT subsets are co-expressed with PD-1/HLA-DR/ICOS/CD45RO and affect the immune status of the microenvironment (Zheng et al., 2020).