Dipping into the cytosol to broaden the MHC class II peptide repertoire.

A new study by Zhou et al. (2005) in this issue of Immunity explores how cytoplasmic autoantigens gain access to the MHC class II antigen-processing pathway. Their experiments show that hsc70 and Lamp-2a mediate antigen transport into endosomal compartments for presentation by MHC class II.