The complex route to MHC class I-peptide complexes.
Elliott T., Neefjes J.
The loading of peptides into the groove of MHC class I molecules prior to antigen presentation is a complex process. In this issue of Cell, Park et al. (2006) show that peptide loading gets a helping hand from a resident ER enzyme called protein disulfide isomerase, a chaperone that has oxidoreductase activity.