CTLA4 and neoplasm: Compared with T cells, the study of immune checkpoints of B cells in tumors is still in its infancy [80], but it has been found that many immune checkpoints on the surface of B cells in the TME are upregulated, such as CTLA-4 [81], TIGIT [82], PD-L1 [83], TIM-1 [84], etc., which affects the functions of B cells, such as proliferation, differentiation, antigen presentation, and antibody production [85], and renders the anti-tumor effects of B cells ineffective.