The impact of DM on MHC class II–restricted antigen presentation can be altered by manipulation of MHC–peptide kinetic stability

DM edits the peptide repertoire presented by major histocompatibility complex class II molecules by professional antigen-presenting cells (APCs), favoring presentation of some peptides over others. Despite considerable research by many laboratories, there is still significant uncertainty regarding the biochemical attributes of class II–peptide complexes that govern their susceptibility to DM editing. Here, using APCs that either do or do not express DM and a set of unrelated antigens, we found that the intrinsic kinetic stability of class II–peptide complexes is tightly correlated with the effects of DM editing within APCs. Furthermore, through the use of kinetic stability variants of three independent peptides, we demonstrate that increasing or decreasing the kinetic stability of class II–peptide complexes causes a corresponding alteration in DM editing. Finally, we show that the spontaneous kinetic stability of class II complexes correlates directly with the efficiency of presentation by DM⁺ APCs and the immunodominance of that class II–peptide complex during an immune response. Collectively, these results suggest that the pattern of DM editing in APCs can be intentionally changed by modifying class II–peptide interactions, leading to the desired hierarchy of presentation on APCs, thereby promoting recruitment of CD4 T cells specific for the preferred peptides during an immune response.