A diverse set of oligomeric class II MHC-peptide complexes for probing T-cell receptor interactions.
BACKGROUND
T-cells are activated by engagement of their clonotypic cell surface receptors with peptide complexes of major histocompatibility complex (MHC) proteins, in a poorly understood process that involves receptor clustering on the membrane surface. Few tools are available to study the molecular mechanisms responsible for initiation of activation processes in T-cells.


RESULTS
A topologically diverse set of oligomers of the human MHC protein HLA-DR1, varying in size from dimers to tetramers, was produced by varying the location of an introduced cysteine residue and the number and spacing of sulfhydryl-reactive groups carried on novel and commercially available cross-linking reagents. Fluorescent probes incorporated into the cross-linking reagents facilitated measurement of oligomer binding to the T-cell surface. Oligomeric MHC-peptide complexes, including a variety of MHC dimers, trimers and tetramers, bound to T-cells and initiated T-cell activation processes in an antigen-specific manner.


CONCLUSIONS
T-cell receptor dimerization on the cell surface is sufficient to initiate intracellular signaling processes, as a variety of MHC-peptide dimers differing in intramolecular spacing and orientation were each able to trigger early T-cell activation events. The relative binding affinities within a homologous series of MHC-peptide oligomers suggest that T-cell receptors may rearrange in the plane of the membrane concurrent with oligomer binding.
Cochran
J R
JR
Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
Stern
L J
LJ
D000595:Amino Acid Sequence; D003545:Cysteine; D015798:HLA-DR1 Antigen / Q000737:chemistry*; D006801:Humans; D008213:Lymphocyte Activation / Q000187:drug effects / Q000276:immunology; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000737:chemistry* / Q000494:pharmacology; D017433:Protein Structure, Secondary; D011948:Receptors, Antigen, T-Cell / Q000737:chemistry* / Q000276:immunology*; D013601:T-Lymphocytes / Q000276:immunology*
D015798:HLA-DR1 Antigen; D010446:Peptide Fragments; D011948:Receptors, Antigen, T-Cell; D003545:Cysteine