CD4 and neoplasm: Cao et al. [67] reported that the observed tumor promoting property associated with IL-35 is mediated via the inhibition of anti-tumor cytotoxic T lymphocyte (CTL) responses which is driven by CD4+ CD25+ Tregs recruitment at malignant sites in addition to the build-up of myeloid derived suppressor cells (MDSC) in the tumor microenvironment [66,67].