Cutting edge: CTLs rapidly capture membrane fragments from target cells ina TCR signaling-dependent manner

Upon encounter of a CTL with a target cell carrying foreign Ags, the TCR in ternalizes with its ligand, the peptide-MHC class I complex. However, it is unclear how this can happen mechanistically because MHC molecules are anch ored to the target cell's surface via a transmembrane domain. By using anti genic peptides and lipids that were fluorescently labeled, we found that CT Ls promptly capture target cell membranes together with the antigenic pepti de as well as various other surface proteins. This efficient and specific c apture process requires sustained TCR signaling. Our observations indicate that this process allows efficient acquisition of the Ag by CTL, which may in turn regulate lymphocyte activation or elimination.