A case for chaperones in antigen processing.

The assembly of peptide-MHC-class-II molecule complexes by antigen-presenting cells is far more efficient than would be predicted from studies of peptide binding to purified MHC class II molecules in vitro. One possible explanation for this discrepancy is that proteins in the antigen-presenting cell facilitate the assembly process. Here, Diane DeNagel and Susan Pierce present the case for involvement of members of the chaperone/heat shock protein 70 family in the intracellular assembly of processed-antigen-MHC-class-II-molecule complexes.