Editors' ChoiceImmunology

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Science Signaling  14 Jul 2009:
Vol. 2, Issue 79, pp. ec239
DOI: 10.1126/scisignal.279ec239

The presentation of exogenous antigens by major histocompatibility complex (MHC) class I molecules is referred to as cross-presentation. Cross-presentation by dendritic cells plays a central role in the priming of cytolytic T lymphocyte responses to natural and vaccine antigens and also in the initiation of autoimmune diseases such as type 1 diabetes. A satisfactory cell biological model of cross-presentation is not available, which would be required to decipher the link, inherent in cross-presentation, between the secretory and the endocytic pathways. Saveanu et al. identify an aminopeptidase, insulin-regulated aminopeptidase (IRAP), which interacts directly with MHC class I molecules. IRAP plays an exclusive and important role in MHC class I cross-presentation of receptor-targeted and phagocytosed antigens. In particular, a specific endosomal compartment, which carries IRAP as a unique marker, is implicated in cross-presentation of phagocytosed antigens.

L. Saveanu, O. Carroll, M. Weimershaus, P. Guermonprez, E. Firat, V. Lindo, F. Greer, J. Davoust, R. Kratzer, S. R. Keller, G. Niedermann, P. van Endert, IRAP identifies an endosomal compartment required for MHC class I cross-presentation. Science 325, 213–217 (2009). [Abstract] [Full Text]