Linked Life Data

2169757

Source:http://linkedlifedata.com/resource/pubmed/id/2169757

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
5
pubmed:dateCreated
1990-11-19
pubmed:abstractText
The antibody response to protein antigens requires specific cooperation between B and T cells. In order to deliver the helper signal, T cells must recognize, in the context of Class II MHC, processed antigen on the membrane of B cells. Processed antigen is in the form of peptides bound in a given site of the Class II MHC molecule; in order to address the question of where, in the B cell, the complex of Class II MHC and processed antigen is formed, we studied the subcellular localization of these two molecules. Since the formation of this complex is the crucial step in antigen processing and presentation, the answer to this question is central to the whole problem of the physiology of antigen handling by B cells. To collect information pertinent to the question, we have compared, in B cells, the intracellular traffic of Class II MHC and of monovalent and divalent anti-immunoglobulin antibodies used as protein ligands of the membrane immunoglobulins. We have done so by two-color immunofluorescence microscopy, and we have detected extensive confluence of Class II MHC molecules with the immunoglobulin ligand, both mono- and bi-valent, in the endosomes of LPS-activated murine B cells. Whereas the ligand clearly reaches the endosomes by internalization from the cell membrane, the Class II MHC molecules could reach the same location either by endocytosis from the membrane or through targeting to the endosomes of newly synthesized Class II MHC molecules. We have collected quantitative evidence for endocytosis of Class II MHC by following, with the fluorescence activated cell sorter, the quenching of the fluorescence of fluoresceinated Fab' anti Class II MHC in LPS-activated murine B cells; this quenching indicates the entry of the label into an acidic intracellular compartment. Together with the results of others, obtained with different methods, our observations support the concept that, at least in mature activated B cells, Class II MHC molecules reach the organelles where they meet processed protein antigens, mainly through the endocytic route. Since activated B cells endocytose their membrane Class II MHC, and not their membrane Class I, our results contribute to the understanding of how B cells present antigens, that have bound to their membrane immunoglobulins, to Class II-restricted helper T cells and not to Class I-restricted cytolytic T cells.
pubmed:grant
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:issn
0724-6803
pubmed:author
pubmed:issnType
Print
pubmed:volume
4
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
255-66; discussion 266-8
pubmed:dateRevised
2007-11-14
pubmed:meshHeading
pubmed-meshheading:2169757-Animals, pubmed-meshheading:2169757-Antibodies, Monoclonal, pubmed-meshheading:2169757-B-Lymphocytes, pubmed-meshheading:2169757-Cells, Cultured, pubmed-meshheading:2169757-Chloroquine, pubmed-meshheading:2169757-Cytosol, pubmed-meshheading:2169757-Endocytosis, pubmed-meshheading:2169757-Flow Cytometry, pubmed-meshheading:2169757-Histocompatibility Antigens Class II, pubmed-meshheading:2169757-Hydrogen-Ion Concentration, pubmed-meshheading:2169757-Immunoglobulin Fab Fragments, pubmed-meshheading:2169757-Kinetics, pubmed-meshheading:2169757-Lipopolysaccharides, pubmed-meshheading:2169757-Lymphocyte Activation, pubmed-meshheading:2169757-Mice, pubmed-meshheading:2169757-Mice, Inbred A, pubmed-meshheading:2169757-Mice, Inbred BALB C, pubmed-meshheading:2169757-Microscopy, Fluorescence, pubmed-meshheading:2169757-Spleen
pubmed:year
1990
pubmed:articleTitle
Class II MHC molecules are spontaneously internalized in acidic endosomes by activated B cells.
pubmed:affiliation
Department of Microbiology, College of Physicians and Surgeons, Columbia University, New York, NY 10032.
pubmed:publicationType
Journal Article, Research Support, U.S. Gov't, P.H.S.