A cell-free model system for the study of antigen processing

Antigen processing is an essential step in the presentation of most protein antigens to class 2 MHC restricted T cells, but many of the details of processing remain unknown. In this study we show that a whole cell lysate, as well as membrane fractions from an antigen-presenting B cell lymphoma, can process ovalbumin. In this system native ovalbumin incubated with these membranes at acidic pH can be presented to an antigen-specific hybridoma by gluteraldehyde-fixed, antigen-presenting cells. This processing is inhibited by pepstatin, a selective inhibitor of aspartyl proteases. This is the first study of processing by subcellular fractions, and this cell-free system will provide a good model in which to dissect further the molecular requirements of antigen processing.