ANALYSIS OF SUBCELLULAR ORGANELLES INVOLVED IN MAJOR HISTOCOMPATIBILITY COMPLEX (MHC) CLASS II-RESTRICTED ANTIGEN PRESENTATION BY ELECTROPHORESIS

Presentation of material derived from pathogenic organisms to the immu ne system requires uptake of antigens into antigen presenting cells, p rocessing into peptide fragments and loading of the resulting fragment s onto major histocompatibility complex (MHC) class II molecules. MHC class II-restricted antigen presentation involves both the biosyntheti c as well as the endocytic pathway of antigen-presenting cells. In rec ent years, the general mechanisms that govern these processes have bee n delineated, and specialized organelles have been characterized in wh ich processing and loading of antigens takes place. Here, we review th e work that has led to the characterization of these MHC class II comp artments, and describe the use of organelle electrophoresis and two-di mensional gel electrophoresis to analyze the molecular composition of the different subcellular organelles involved in MHC class II-restrict ed antigen presentation as well as in antigen uptake.