Aparna Raval, Ph.D. Heather Lazusky, B.S . I molecules, which function as receptors for intracellular derived peptide antigens. Binding to class I molecules of peptides derived from viruses or other intracellular invaders triggers cellular immune responses. To fulfill their role as sentinels of cellular distress, MHC class I molecules are expressed in nearly all somatic tissues. However, levels of class I expression vary markedly among the tissues, ranging from high expression in the lymphoid compartment to very low levels in kidney, liver and endocrine tissues.
Levels also vary within an individual cell type, depending upon the physiological state.
We have postulated that this optimal level will differ among different tissues under different physiological conditions. I expression appropriately would result in dysregulation of the immune system. Thus, repression of class I expression by viral mediators may permit accumulation of a reservoir of virally infected cells, which are invisible to the immune system and the potential source of cancers. Conversely, overexpression of class I may lead to activation of autoreactive cells and the generation of autoimmune disease. Given the importance of the MHC class I genes in the immune response, it is important to understand the molecular mechanisms that underlie their transcriptional regulation.