g. the expression of inhibitory receptors such as PD-1 [18–20], the immunosuppressive tumor microenvironment [21, 22], the lack of sufficient CD4+ T-cell help [18, 19] or the action of suppressive cytokines [21], regulatory T cells or myeloid derived suppressor cells [17, 19, 21, 22] have been suggested to contribute. The gene discussed is CD4; the disease is neoplasm.