Stability of surface H-2K(b), H-2D(b), and peptide-receptive H-2K(b) on splenocytes.
We have used flow cytometry to study the stability and peptide-binding capability of MHC class I (MHC-I) on the surface of normal C57BL/6 mouse T lymphoblasts. The MHC-I molecules on each cell are nearly evenly divided into two populations with mean half-life values of approximately 1 and 20 h. Our observations suggest that members of the later contain peptide bound with medium to high affinity. Cell surface MHC-I molecules capable of binding exogenous peptide (thus, "peptide-receptive") belong almost entirely to the less stable population. Before exogenous peptide can bind, MHC-I must undergo a change, probably loss of a very low affinity peptide. For MHC-I-K(b), we found that the maximum rate for binding of exogenous peptide corresponds to a t(1/2) value of 12 min. To maintain the 50:50 steady-state distribution of long- vs short-lived MHC-I molecules on the cell surface, approximately 20 short-lived molecules must be exported to the cell surface for each long-lived molecule.
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Ontario Cancer Institute, Department of Medical Biophysics, University of Toronto, Toronto, Ontario, Canada.
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D000818:Animals; D000950:Antigens, Ly; D020126:Brefeldin A / Q000494:pharmacology; D002352:Carrier Proteins / Q000502:physiology; D006183:H-2 Antigens / Q000737:chemistry* / Q000378:metabolism; D006207:Half-Life; D064532:Histocompatibility Antigen H-2D; D037181:Lectins, C-Type; D008565:Membrane Proteins / Q000502:physiology; D051379:Mice; D008810:Mice, Inbred C57BL; D010455:Peptides / Q000378:metabolism*; D011487:Protein Conformation; D055630:Receptors, NK Cell Lectin-Like; D013154:Spleen / Q000166:cytology; D013601:T-Lymphocytes / Q000378:metabolism*
D000950:Antigens, Ly; D002352:Carrier Proteins; D006183:H-2 Antigens; C032876:H-2Kb protein, mouse; D064532:Histocompatibility Antigen H-2D; D037181:Lectins, C-Type; D008565:Membrane Proteins; D010455:Peptides; D055630:Receptors, NK Cell Lectin-Like; D020126:Brefeldin A