Intracellular surveillance: controlling the assembly of MHC class I-peptide complexes.

MHC class I molecules bind with high affinity to peptides in the endoplasmic reticulum and display them on the cell surface. Here they are screened by CD8-positive T-lymphocytes for the presence of foreign, pathogen-derived peptides within the mass of self-peptides expressed. MHC class I assembly is a complicated process involving a number of accessory molecules, including specialized components as well as common chaperones. Our understanding of the mechanisms involved, while quite advanced, is far from complete.