PVR and neoplasm: Mechanistically, CD44 reduced the sensitivity of tumour cells to CTLs by downregulating the Fas-FasL pathway, causing tumours to escape CTL killing; CEACAM1 affected the immune tolerance of T cells through the TIM-3 signalling pathway and suppressed the immune response of T cells to cancer cells; both SIGLEC6 and HMGB1 played an immunosuppressive function on CTLs by regulating the activity of mast cells; and CD155 and NECTIN2 are both members of the Nectin-like molecule family, which affect the activity of CTLs, thereby inhibiting antitumour immunity (Supplementary Table 2).