PDCD1 and nonpapillary renal cell carcinoma: In addition to PD-1, this proliferative subset of CD8+ T cells in ccRCC had increased levels of CTLA-4, ICOS, 4-1BB (CD137), TIM-3, HLA-DR, and CD38 compared to the other CD45+ CD3+ CD8+ T cells (Fig. 6e).