Clustering of Class I HLA Oligomers with CD8 and TCR: Three-Dimensional Models Based on Fluorescence Resonance Energy Transfer and Crystallographic Data

• Published in: The Journal of immunology (1950) Vol. 166; no. 8; pp. 5078 - 5086
• Main Authors: Gaspar, Rezso, Jr, Bagossi, Peter, Bene, Laszlo, Matko, Janos, Szollosi, Janos, Tozser, Jozsef, Fesus, Laszlo, Waldmann, Thomas A, Damjanovich, Sandor
• Format: Journal Article
• Language: English
• Published: United States Am Assoc Immnol 15-04-2001
• Subjects: Antigen-Presenting Cells - chemistry; Antigen-Presenting Cells - immunology; B-Lymphocytes - chemistry; B-Lymphocytes - immunology; beta 2-Microglobulin - chemistry; CD8 antigen; CD8 Antigens - chemistry; Cell Line, Transformed; Cell Membrane - chemistry; Cell Membrane - immunology; Computer Simulation; Crystallography, X-Ray - methods; Energy Transfer - immunology; Epitopes, B-Lymphocyte - chemistry; histocompatibility antigen HLA; Histocompatibility Antigens Class I - chemistry; HLA Antigens - chemistry; HLA-A2 Antigen - chemistry; Humans; Immunoglobulin Fab Fragments - chemistry; Models, Molecular; Peptide Mapping; Receptors, Antigen, T-Cell - chemistry; Spectrometry, Fluorescence - methods
• ISSN: 0022-1767; 1550-6606
• DOI: 10.4049/jimmunol.166.8.5078

Fluorescence resonance energy transfer (FRET) data, in accordance with lateral mobility measurements, suggested the existence of class I HLA dimers and oligomers at the surface of live human cells, including the B lymphoblast cell line (JY) used in the present study. Intra- and intermolecular class I HLA epitope distances were measured on JY B cells by FRET using fluorophore-conjugated Ag-binding fragments of mAbs W6/32 and L368 directed against structurally well-characterized heavy and light chain epitopes, respectively. Out-of-plane location of these epitopes relative to the membrane-bound BODIPY-PC (2-(4,4-difluoro-5-(4-phenyl-1,3-butadienyl)-4-bora-3a,4a-diaza-s-indacene-3-pentanoyl)-1-hexadecanoyl-sn-glycero-3-phosphocholine) was also determined by FRET. Computer-simulated docking of crystallographic structures of class I HLA and epitope-specific Ag-binding fragments, with experimentally determined interepitope and epitope to cell surface distances as constraints, revealed several sterically allowed and FRET-compatible class I HLA dimeric and tetrameric arrangements. Extension of the tetrameric class I HLA model with interacting TCR and CD8 resulted in a model of a supramolecular cluster that may exist physiologically and serve as a functionally significant unit for a network of CD8-HLA-I complexes providing enhanced signaling efficiency even at low MHC-peptide concentrations at the interface of effector and APCs.