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. 2019 Oct 18;39(10):BSR20193220. doi: 10.1042/BSR20193220

Figure 1. An overview of the mechanisms of antigen cross-presentation.

Figure 1

Vacuolar and Cytosolic cross-presentation pathways inside a DC: (1) Antigens internalized through phagocytosis or receptor-mediated endocytosis are properly degraded in the endosomes due to varying pH and different proteases. (2) Antigen is loaded on to recycled MHC I in the phagosome. (3) The recycling of MHC I is mediated through Rab11a in Toll-like receptor (TLR) controlled process with the help of SNAP23 dependent on MyD88 signaling. (4) Alternatively, antigens processed under the cytosolic pathway are translocated to the cytosol via phagosomal disruption through NOX-2 complex and through Sec 61 translocon. (5) The antigens are lysed by proteasome complex. (6) Lysed antigens are transported to the ER via TAP transporter and further trimmed by ERAP and loaded on to MHC I. (7) Antigenic peptide in the cytosol after proteasomal degradation may also get retransported into phagosome through TAP which is further trimmed by IRAP and presented on to recycled MHC-I molecule. (8) TAP molecule is transported from ER with the help of Sec22b protein resident of the ERGIC that interacts with Syntaxin 4 on phagosome. Abbreviation: ERGIC, ER-Golgi intermediate compartment.