HAVCR2 and neoplasm: Many studies have reported that tumor-derived exosomes (TEXs) are enriched in immuno-oncological proteins, including T-cell immune checkpoints such as PD-L1, cytotoxic T-lymphocyte-associated antigen 4 (CTLA-4), T-cell immunoglobulin mucin-3(TIM-3) and NK immune checkpoints such as MHC class I chain-related protein A (MICA), MHC class I chain-related protein B (MICB), UL16 binding protein 1 (ULBP1) and UL16 binding protein 2 (ULBP2) (26–29).