TY - JOUR
T1 - Functional and ultrastructural evidence for intracellular formation of major histocompatibility complex class II-peptide complexes during antigen processing
AU - Harding, Clifford V.
AU - Unanue, Emil R.
AU - Slot, Jan W.
AU - Schwartz, Alan L.
AU - Geuze, Hans J.
PY - 1990
Y1 - 1990
N2 - Antigen presentation requires intracellular processing of native antigens to produce immunogenic peptides that bind to major histocompatibility complex class II (MHC-II) molecules. In functional studies of antigen processing by elicited peritoneal macrophages, MHC-II-peptide complexes were formed intracellularly. Immunogenic peptides were not released to bind surface MHC-II molecules. Ultrastructural studies employing immunogold staining in ultrathin cryosections of these macrophages showed large amounts of MHC-II molecules in intracellular sac-like vacuoles in the peripheral cytoplasm; most of these were negative for the lamp 1 lysosomal/endosomal membrane protein and cathepsin D. MHC-II molecules were also present in endosomes containing cathepsin D and lamp 1 as well as previously internalized gold-transferrin. The intracellular pool of MHC-II molecules was only slightly decreased by treatment with cycloheximide for 3 hr, indicating that it consisted mainly of endocytosed, recycling molecules, as opposed to nascent ones. These ultrastructural studies support the notion that there is endocytosis of MHC-II molecules into endocytic compartments, consistent with our earlier biochemical data. Furthermore, we have defined the distinct endocytic compartments that must mediate important functions in antigen processing, including the formation of MHC-II-peptide complexes.
AB - Antigen presentation requires intracellular processing of native antigens to produce immunogenic peptides that bind to major histocompatibility complex class II (MHC-II) molecules. In functional studies of antigen processing by elicited peritoneal macrophages, MHC-II-peptide complexes were formed intracellularly. Immunogenic peptides were not released to bind surface MHC-II molecules. Ultrastructural studies employing immunogold staining in ultrathin cryosections of these macrophages showed large amounts of MHC-II molecules in intracellular sac-like vacuoles in the peripheral cytoplasm; most of these were negative for the lamp 1 lysosomal/endosomal membrane protein and cathepsin D. MHC-II molecules were also present in endosomes containing cathepsin D and lamp 1 as well as previously internalized gold-transferrin. The intracellular pool of MHC-II molecules was only slightly decreased by treatment with cycloheximide for 3 hr, indicating that it consisted mainly of endocytosed, recycling molecules, as opposed to nascent ones. These ultrastructural studies support the notion that there is endocytosis of MHC-II molecules into endocytic compartments, consistent with our earlier biochemical data. Furthermore, we have defined the distinct endocytic compartments that must mediate important functions in antigen processing, including the formation of MHC-II-peptide complexes.
KW - Endocytosis
KW - Endosomes
KW - Immunocytochemistry
UR - http://www.scopus.com/inward/record.url?scp=0024991936&partnerID=8YFLogxK
U2 - 10.1073/pnas.87.14.5553
DO - 10.1073/pnas.87.14.5553
M3 - Article
C2 - 2371288
AN - SCOPUS:0024991936
SN - 0027-8424
VL - 87
SP - 5553
EP - 5557
JO - Proceedings of the National Academy of Sciences of the United States of America
JF - Proceedings of the National Academy of Sciences of the United States of America
IS - 14
ER -