Potent T cell agonism mediated by a very rapid TCR/pMHC interaction

Abstract

The interaction between T cell receptors (TCR) and peptide-major histocompatibility complex (pMHC) antigens can lead to varying degrees of agonism (T cell activation), or antagonism. The P14 TCR recognises the lymphocytic choriomeningitis virus (LCMV)-derived peptide, gp33 residues 33-41 (KAVYNFATC), presented in the context of H-2D(b). The cellular responses to various related H-2D(b) peptide ligands are very well characterised, and P14 TCR-transgenic mice have been used extensively in models of virus infection, autoimmunity and tumour rejection. Here, we analyse the binding of the P14 soluble TCR to a broad panel of related H-2D(b)-peptide complexes by surface plasmon resonance, and compare this with their diverse cellular responses. P14 TCR binds H-2D(b)-gp33 with a KD of 3 microM (+/-0.5 microM), typical of an immunodominant antiviral TCR, but with unusually fast kinetics (k(off) = 1 s(-1)), corresponding to a half-life of 0.7 s at 25 degrees C, outside the range previously observed for murine agonist TCR/pMHC interactions. The most striking feature of these data is that a very short half-life does not preclude the ability of a TCR/pMHC interaction to induce antiviral immunity, autoimmune disease and tumour rejection.

Figure 1

(A)Binding of P14 soluble TCR to H-2D^b-gp33 peptide measured by SPR. Background responses to the control flow cell were subtracted and all data were plotted with the injection point at 0s. (B)Equilibrium binding of soluble P14 TCR to H-2D^b-gp33 peptide. (C)Arrhenius analysis of dissociation kinetics for the P14 TCR binding to H-2D^b-gp33; Arrhenius dissociation energy. ▵E_a^diss = 13kcal/mol. (D)SPR binding of soluble P14 TCR binding to H-2D^b-gp33 at various temperatures. (E)Plot of ▵G against temperature along with a least-squares fit of the equation ▵G°_T =▵H° +▵C_P(T–T₀) –T▵S° –T▵C_Pln(T/T₀) to provide an estimate of ▵Cp.

Figure 2

Equilibrium binding of P14 soluble TCR to H-2D^b complexed with various altered peptide ligands measured by Biacore 3000 SPR at 25°C. Peptide abbreviations as in Table 1.

Figure 3

Binding affinities of P14 and the various APL were plotted against %TCR down-regulation observed upon stimulation with each peptide at 10^–6M concentration. The correlation coefficient was calculated as 0.63, using Excel software (p<0.01).