CD4 and neoplasm: In the tumour microenvironment, IFN-γ, which is produced by cytotoxic CD8+ and CD4+ Th1 T cells, is considered the major anti-tumour immune effectors, whereas the cytokines IL-6, TNF, IL-1β, and IL-23, which are produced by tumour-associated macrophages or myeloid-derived suppressive cells, are generally recognized as dominant tumour-promoting factors [25].