CHEMICAL CHAPERONES ENHANCE SUPERANTIGEN AND CONVENTIONAL ANTIGEN PRESENTATION BY HLA-DM-DEFICIENT AS WELL AS HLA-DM-SUFFICIENT ANTIGEN-PRESENTING CELLS AND ENHANCE IGG2A PRODUCTION IN-VIVO

Chemical chaperones, first defined in studies of mutant cystic fibrosi s transmembrane conductance regulator proteins, are small molecules th at act as stabilizers of proteins in their native state and have the a bility in some cases to rescue protein-folding mutants within cells, K LA-DM is an MHC II-specific molecular chaperone that facilitates pepti de loading onto MHC It proteins and also stabilizes empty MHC II molec ules prior to their acquisition of antigenic peptides. APC that lack H LA-DM exhibit quantitative defects in protein Ag as well as superantig en presentation. Here we show that both the superantigen and protein p resentation defect in MHC II-transfected, HLA-DM-deficient T2 cells ca n be partially overcome by treating the APC with the chemical chaperon es glycerol, DMSO, or trimethylamine oxide. These chemical chaperones also enhance superantigen and conventional Ag presentation by wild-typ e APC, In vivo, glycerol was found to act as an adjuvant and resulted in enhanced IgG2a production to trinitrophenyl-keyhole limpet hemocyan in (TNP-KLH), In vitro, the enhancement of Ag presentation by chemical chaperones was found to take place at the level of the APC and took s everal hours to develop. Subcellular fractionation experiments show th at HLA-DM enhances presentation of peptides by dense endosome fraction s whereas chemical chaperones enhance presentation by light membrane f ractions (early endosome or plasma membrane). The mechanism by which t hese chemical chaperones augment Ag presentation is not defined, but f low cytometric analysis suggests that the enhancement may be due to a subtle effect on the stability of several different proteins at the ce ll surface.