STRUCTURE OF PEPTIDES ASSOCIATED WITH CLASS-I AND CLASS-II MHC MOLECULES

Class I and class II molecules encoded by genes within the major histo compatibility complex play a central role in regulation of immune resp onses through their ability to bind and display small peptides derived from foreign antigens. Within the last few years, considerable progre ss has been made in understanding the structures of class T and class II MHC molecules, as well as the features of the peptides that are the ir principal ligands. This review summarizes this information and desc ribes how it accounts for both the specificity and degeneracy of pepti de binding. It also considers how the origin and structural features o f peptides that have been isolated from MHC molecules, so-called ''nat urally processed'' peptides, have provided insight into the pathways t hrough which the peptides are produced. Finally, the use of new struct ural information and techniques for peptide characterization for the i dentification of peptides that comprise epitopes for individual antige n-specific T cells an considered.