PDCD1 and neoplasm: Likewise, tumor-infiltrating CMV-specific T cells express augmented levels of inhibitory receptors programmed cell death protein 1 (PD-1), T cell immunoglobulin and mucin-domain containing molecule-3 (TIM-3), and cytotoxic T-lymphocyte-associated antigen 4 (CTLA-4) and lower levels of transcription factors T-bet, eomesodermin (EOMES), and lymphoid enhancer-binding factor 1 (LEF-1), while having a 4-fold lower frequency in tumor tissue compared to T cells circulating in peripheral blood (125).