CD4 and cancer: In a recent study on spontaneous and transplantable tumor-bearing mice, the tumor-evoked regulatory B cells (tBregs), a lymphocyte subpopulation that derives from TDSF-conditioned B cells, induced the differentiation of CD4+ T cells into Tregs and fully activated the prometastatic functions of cancer-primed MDSCs through the TGF-β signaling, eventually increasing metastasis [36,54].