title: Kinetics and mechanics of two-dimensional interactions between T cell receptors and different activating ligands.
abstract: Adaptive immune responses are driven by interactions between T cell antigen receptors (TCRs) and complexes of peptide antigens (p) bound to Major Histocompatibility Complex proteins (MHC) on the surface of antigen-presenting cells. Many experiments support the hypothesis that T cell response is quantitatively and qualitatively dependent on the so-called strength of TCR/pMHC association. Most available data are correlations between binding parameters measured in solution (three-dimensional) and pMHC activation potency, suggesting that full lymphocyte activation required a minimal lifetime for TCR/pMHC interaction. However, recent reports suggest important discrepancies between the binding properties of ligand-receptor couples measured in solution (three-dimensional) and those measured using surface-bound molecules (two-dimensional). Other reports suggest that bond mechanical strength may be important in addition to kinetic parameters. Here, we used a laminar flow chamber to monitor at the single molecule level the two-dimensional interaction between a recombinant human TCR and eight pMHCs with variable potency. We found that 1), two-dimensional dissociation rates were comparable to three-dimensional parameters previously obtained with the same molecules; 2), no significant correlation was found between association rates and activating potency of pMHCs; 3), bond mechanical strength was partly independent of bond lifetime; and 4), a suitable combination of bond lifetime and bond strength displayed optimal correlation with activation efficiency. These results suggest possible refinements of contemporary models of signal generation by T cell receptors. In conclusion, we reported, for the first time to our knowledge, the two-dimensional binding properties of eight TCR/pMHC couples in a cell-free system with single bond resolution.
authors.affiliation: Lab Adhesion and Inflammation, INSERM, U 1067, Marseille, France.
authors.forename: Philippe
authors.initials: P
authors.lastname: Robert
authors.forename: Milos
authors.initials: M
authors.lastname: Aleksic
authors.forename: Omer
authors.initials: O
authors.lastname: Dushek
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Cerundolo
authors.forename: Pierre
authors.initials: P
authors.lastname: Bongrand
authors.forename: P Anton
authors.initials: PA
authors.lastname: van der Merwe
mesh_terms: D006680:HLA Antigens / Q000378:metabolism*; D006801:Humans; D007700:Kinetics; D008024:Ligands; D010455:Peptides / Q000378:metabolism; D011485:Protein Binding; D011948:Receptors, Antigen, T-Cell / Q000378:metabolism*; D013379:Substrate Specificity
chemical_list: D006680:HLA Antigens; D008024:Ligands; D010455:Peptides; D011948:Receptors, Antigen, T-Cell