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Extensive peptide ligand exchange by surface class I major histocompatibility complex molecules independent of exogenous beta 2-microglobulin.
- Source :
-
Proceedings of the National Academy of Sciences of the United States of America [Proc Natl Acad Sci U S A] 1992 Aug 15; Vol. 89 (16), pp. 7767-71. - Publication Year :
- 1992
-
Abstract
- Certain class I major histocompatibility complex molecules expressed on live cells have been shown to bind exogenous peptide ligands. However, it remains controversial whether this binding occurs by peptide exchange or to empty surface class I molecules. In this report we compare the surface binding and dissociation of two virus-derived ligands of the Ld class I molecule of the mouse. The peptide ligands were previously identified in immune responses to cytomegalovirus or lymphochoriomeningitis virus as immunodominant, optimally sized, and Ld restricted. Ligand dissociation was monitored on live cells indirectly by measuring the surface turnover of Ld-peptide complexes or directly by using labeled peptides. The cytomegalovirus-derived and lymphochoriomeningitis virus-derived peptides appeared to dissociate relatively rapidly; however, the cytomegalovirus-derived peptide had a more rapid off-rate than the lymphochoriomeningitis-derived peptide. Furthermore, these rates of dissociation appear to span that seen with endogenous Ld-associated peptides expressed by cells at 37 degrees C. Exploiting the extraordinary accessibility of the surface Ld ligand binding site we developed an assay to quantitate peptide ligand exchange. Cells were precoated with saturating amounts of unlabeled peptide by overnight incubation and were then tested for secondary binding of labeled peptides in a 4-h assay. Our results unequivocally demonstrate the potential for surface class I molecules to undergo peptide exchange. Furthermore, peptide exchange was found to be largely independent of exogenous beta 2-microglobulin. This result implies that beta 2-microglobulin association and not beta 2-microglobulin exchange is the critical factor in peptide exchange by surface class I molecules. Because of the exquisite ability of T cells to discriminate different amounts of ligand bound to class I, the binding of exogenous peptides could play a critical role in normal or aberrant immune responses.
- Subjects :
- Animals
Antibodies, Monoclonal
Cell Line
Cell Membrane immunology
Cytomegalovirus immunology
Flow Cytometry
Histocompatibility Antigens Class I genetics
Humans
Kinetics
Ligands
Lymphocytic choriomeningitis virus immunology
Mice
Peptides chemical synthesis
Peptides metabolism
Protein Binding
T-Lymphocytes, Cytotoxic immunology
Temperature
Time Factors
Transfection
Histocompatibility Antigens Class I metabolism
beta 2-Microglobulin metabolism
Subjects
Details
- Language :
- English
- ISSN :
- 0027-8424
- Volume :
- 89
- Issue :
- 16
- Database :
- MEDLINE
- Journal :
- Proceedings of the National Academy of Sciences of the United States of America
- Publication Type :
- Academic Journal
- Accession number :
- 1323851
- Full Text :
- https://doi.org/10.1073/pnas.89.16.7767