CD4 and prostate cancer: The prostate cancer immune microenvironment is shown to be immunosuppressive, as shown by the recruitment and accumulation of T regulatory cells (CD4+ Tregs) and TH17 lymphocytes [52, 53], myeloid-derived suppressive cells [54], NK cells (CD65+) with low or no cytotoxic activity, and also elevated levels of secreted TGFβ1 [55].