The genes encoding the major components of the antigen processing and presentation pathway (MHC class II, invariant chain and HLA-DM) are regulated in a coordinate and concerted fashion by a conserved group of transcription factors. The identification and characterization of these transcription factors over the past few years has provided insight into how these important genes and the process of antigen presentation are regulated. Regulation of the antigen processing genes includes mechanisms involving the epigenetic modification of DNA sequences and chromatin, and the control of nuclear import of transcription factors.