The major histocompatibility complex (MHC) constitutes a region of the genome whose gene products are primarily devoted to providing extracellular presentation of intracellular antigens.
Class I MHC molecules interact with a diverse array of self and foreign peptides and act as peptide-binding transport and display proteins. Recognition of foreign antigens causes effector responses by the antigen-specific receptors of T lymphocytes. The most clearly defined role for class I-peptide complexes is to initiate effector response upon binding to antigen-specific receptors on cytotoxic T-cells (CD8+ T-cells).