title: Cloned T cells internalize peptide from bound complexes of peptide and purified class II major histocompatibility complex antigen.
abstract: Antigen presentation to helper T cells involves the formation of a trimolecular complex consisting of a class II major histocompatibility complex (MHC) antigen combined with an antigenic peptide on the surface of an antigen-presenting cell and a T cell receptor (TCR) on the T cell. The fate of the MHC class II, peptide, or TCR moieties of the ternary complex following antigen presentation is unknown. Using radiolabeled complexes of affinity-purified murine MHC class II molecules and peptides corresponding to T cell epitopes of myelin basic protein (MBP), this report presents evidence that the binding of preformed relevant MHC class II-peptide complexes to cloned T cells in vitro results in internalization of the peptide moiety. Neither the restricting MHC class II molecule nor the TCR moiety of the trimolecular complex was internalized by T cells. The specificity of peptide internalization was demonstrated using complexes of syngeneic MHC class II with an irrelevant MBP peptide analog and by cloned T cells restricted for a different epitope of the same MBP antigen. Furthermore, the peptide translocation mediated by MHC class II and TCR was demonstrated by antibody-blocking experiments using anti-class and anti-TCR monoclonal antibodies. The peptide internalization by T cells was markedly reduced when binding was performed at 4 degrees C as compared with 37 degrees C. In addition, a significant inhibition of peptide translocation was observed in the presence of a metabolic inhibitor (sodium azide) but not in the presence of cytochalasin B. These results together demonstrate that the in vitro interaction of soluble MHC II-peptide complexes with cloned T cells is an active process associated with uptake of the antigenic peptide.
authors.affiliation: Anergen Inc., Redwood City, California 94063.
authors.forename: B
authors.initials: B
authors.lastname: Nag
authors.forename: S V
authors.initials: SV
authors.lastname: Deshpande
authors.forename: S D
authors.initials: SD
authors.lastname: Sharma
authors.forename: B R
authors.initials: BR
authors.lastname: Clark
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000911:Antibodies, Monoclonal / Q000494:pharmacology; D002999:Clone Cells; D004705:Endocytosis; D005434:Flow Cytometry; D000949:Histocompatibility Antigens Class II / Q000378:metabolism*; D007700:Kinetics; D046911:Macromolecular Substances; D051379:Mice; D008969:Molecular Sequence Data; D004676:Myelin Basic Protein / Q000378:metabolism*; D010446:Peptide Fragments / Q000138:chemical synthesis / Q000378:metabolism; D010455:Peptides / Q000138:chemical synthesis / Q000378:metabolism*; D051381:Rats; D011948:Receptors, Antigen, T-Cell / Q000187:drug effects / Q000276:immunology / Q000378:metabolism*; D013379:Substrate Specificity; D013601:T-Lymphocytes / Q000276:immunology / Q000378:metabolism*
chemical_list: D000911:Antibodies, Monoclonal; D000949:Histocompatibility Antigens Class II; D046911:Macromolecular Substances; D004676:Myelin Basic Protein; D010446:Peptide Fragments; D010455:Peptides; D011948:Receptors, Antigen, T-Cell