Chaperone Puts The Brakes On

摘要

Dendritic cells function primarily as immune sentinels. In the periphery, they actively scan surrounding interstitial spaces for pathogenic invaders and internalize (through a process called endocy-tosis) foreign antigens present in the extracellular milieu (1). In secondary lymphoid tissues, dendritic cells shift their attention to presenting previously internalized antigen as peptides to T cells, thus alerting the immune system to an impending threat. To carry out the latter function of activating T cells, dendritic cells must migrate from peripheral non-lymphoid tissues to draining lymph nodes, where the likelihood of meeting a rare antigen-specific T cell is highest (2). During this migration, dendritic cells degrade internalized antigen into peptide fragments that are then loaded onto major histocompatibility complex (MHC class Ⅱ) molecules for display at the cell surface. On page 1705 of this issue, Faure-Andre et al. report their unexpected finding that dendritic cell motility is linked to the invariant chain (Ii), a key molecule in antigen processing (3).