CD4 and cancer: Altogether, these mechanisms orchestrate an immunosuppressive cancer microenvironment through inhibition of immune cells involved in tumor rejection—CD4+/CD8+ T lymphocytes and natural killer (NK) cells—together with the recruitment and/or activation of immunosuppressive cells, like CD4+CD25+FoxP3+ T regulatory cells (Tregs), myeloid-derived suppressor cells (MDSCs) and anti-inflammatory M2 macrophages.