CTLA4 and neoplasm: In addition, the interaction of tumour cells with CAR T cells can induce the expression of immunosuppressive molecules, such as CTLA-4, EOMSE and PD1, through signalling pathways that lead to T-cell “exhaustion” or “dysfunction”, and the exhaustion of CAR T cells under long-term antigen stimulation is also a factor in disease recurrence or resistance7.