CD4 and cancer: According to previous studies, regulatory T cells (Tregs) have a high degree of immunosuppressive function and play an important role in maintaining self-tolerance and immune homeostasis; however, in malignant tumors, Tregs, an immunosuppressive subset of CD4 + T cells, can exhibit protumor activity by inhibiting the activation and proliferation of effector T cells, thus limiting the autoimmune response [52, 53].