Smart antigen-presenting cells (APCs) use proteolysis with restraint, according to Lélia Delamarre, Ira Mellman, Sergio Trombetta, and colleagues (Yale University, New Haven, CT). Although perhaps contrary to prevailing assumptions, this less-is-more approach may prevent excessive or premature peptide processing.

“We've been led to believe that, since so many different antigens have to be made, APCs need a large, diverse set of [protease] activities,” says Mellman. But dendritic cells (DCs) and B cells are no more endowed with lysosomal proteases than is the average fibroblast, based on the new results. Of the APCs tested, only macrophages were particularly protease packed.


Delamarre, L., et al.