CD4 and breast cancer: The tumor expressing HLA-II grows slower than the control group, and more functional CD4+ and CD8+ T cells are recruited.[59] The level of HLA-DR in cytotoxic T lymphocytes is an independent and robust predictor of the response of BC patients to neoadjuvant chemotherapy.[60] HLA-DR+ cytotoxic T lymphocytes mainly exist in TME, and produce high-level cytotoxic related molecules, which are negatively correlated with the immunosuppressive characteristics of tumor environment and are systematically reflected.[61]