CD4 and cancer: They can polarize immune responses as T-helper cells (CD4+cells); orchestrate humoral reactions as T-follicular helper cells (a specialized subset of CD4+ cells); modulate the activity of effector cells as Treg cells (there are both CD4+ and CD8+Treg cells); or directly kill targeted cancer cells as cytotoxic T-cells (mainly CD8+ and a small subset of CD4+) (18).