CD4 and neoplasm: The immune-escape phenomenon of tumour cells is also determined by MDSCs which inhibit lymphocyte activity by inducing CD4+CD25+Foxp3+Tregs cells in TME, producing TGF-β, depletion or sequestration of amino acids required for T cell function, or nitration of T cell receptors or chemokine receptors on tumour-specific T cells [49,58].