BETA-2-MICROGLOBULIN RESTRICTION OF ANTIGEN PRESENTATION

ANTIGENS are generally thought to be recognized by cytotoxic T lymphocytes as peptides in the context of class I major histo-compatibility proteins complex1,2, which are heterodimers of heavy chains noncovalently associated with β2-microglobulin (β2m). The highly polymorphic nature of the heavy chains and their resulting ability to present different sets of peptides has presumably evolved to allow potent immune responses against most pathogens. By contrast, the polymorphism of β2m is limited; seven alleles are known in the mouse3,4 and only one has been identified in humans. β2-Microglobulin was consequently thought to have only structural functions: namely, to ensure correct folding of class I molecules and their transport to the cell surface5-9. Although β2m is not implicated directly in the formation of the peptide binding site10,11, we report here that it participates in the selection of MHC class I molecule-associated peptides. © 1990 Nature Publishing Group.