CD4 and neoplasm: Tregs were also found to play a role in inhibiting the proliferation of tumor-specific effector T cells (especially CD8+ and CD4+ T cells) and suppressing the secretion of IFN-γ and IL-2 by effector T cells via expressing intracellular CTLA-4, glucocorticoid—induced tumor necrosis factor receptor (GITR) and FOXP3(54).