Intersection of epigenetics and immune surveillance. Regulation of immune surveillance is controlled in part by epigenetic operations. The histone acetyltransferase enzyme CREBBP activates expression of MHCII, which allows for engagement between the antigen-presenting cell and the T cell. CREBBP also abrogates BCL6, which in turn abrogates PD-L1 expression. These effects have been reversed with HDAC inhibitors. EZH2 is associated with increased CTLA4 activity therefore EZH2 inhibitors have combined favorably with CLTA4 inhibitors. Expression of PD-1, PD-L1, CTLA4, and TIM-3 is controlled by promotor region methylation; therefore, their expression may be modulated by DNMT inhibitors.