The precise regulation of Major Histocompatibility class II (MHC-II) genes plays an important role in the control of the adaptive immune response. MHC-II genes are expressed constitutively in only a few cell types, but their expression can be induced by the inflammatory response cytokine interferon gamma (INF-γ). The regulation of MHC-II is controlled by a Master Regulator, the class II transactivator (CIITA). Multiple studies have shown that CIITA regulated expression of MHC-II is controlled and induced by INF-γ. It has been also shown that a functional CIITA gene is necessary for the expression of MHC-II genes. CIITA is thus a general regulator of both constitutive and inducible MHC-II expression. Although much is known about the transcription factors necessary for CIITA expression, there is little information as to the epigenetic modifications and the requisite enzymes needed to provide these transcription factors access to DNA. Previous studies in the Greer lab have shown that increased levels of acetylation of histones H3 upon INF-γ stimulation, as does tri-methylation of H3K4 upon prolonged cytokine stimulation. Similar observations were made at early time points post IFN-γ stimulation, where there is an instantaneous increase in the levels of H3K18ac and H3K4me3. In contrast to this, the levels of silencing modifications begin to drop with in the first 20 minutes of IFN-γ stimulation. The binding of STAT1 reaches its peak at about 60 minutes and the first transcripts for the protein start to appear as early as 40 minutes post the cytokines stimulation. Our study is the first to link the rapidly occurring epigenetic changes at the CIITA promoter pIV to EZH2