Figure 6. Stochastic reaction-diffusion simulation of time before MCC agonist pMHC escape from TCR clusters, τ_esc (in color; log scale), as a function of τ_off and TCR cluster size.

For small TCR clusters (1–100 TCR molecules) τ_off ≈ τ_esc, indicating no serial rebinding. Only for unrealistically large TCR clusters (1000–10,000 molecules) does ${\tau }_{\mathit{esc}}$ become appreciably longer than ${\tau }_{\mathit{off}}$.

DOI: http://dx.doi.org/10.7554/eLife.00778.013

Figure 6—figure supplement 1. Stochastic reaction-diffusion simulation of time before MCC agonist pMHC escape from TCR clusters.

Simulations of $\frac{{\tau }_{\mathit{esc}}}{{\tau }_{\mathit{off}}}$ as a function of TCR cluster size, ${\tau }_{\mathit{off}}$ , and k_on. The ratio $\frac{{\tau }_{\mathit{esc}}}{{\tau }_{\mathit{off}}}$, which is an indicator of agonist pMHC entrapment, is a function of TCR cluster size and k_on, but not k_off. k_on = 0.51 µm²s⁻¹molecule⁻¹ corresponds to the fastest average k_on that allows for rebinding to the same TCR. Only for unrealistically large TCR cluster sizes (approaching 1000 TCRs per cluster) and fast k_on is $\frac{{\tau }_{\mathit{esc}}}{{\tau }_{\mathit{off}}}\gg 1$, meaning that entrapment due to millisecond-scale unbinding and rebinding is unlikely to result in the minute-scale dwell times observed in our experiments.

DOI: http://dx.doi.org/10.7554/eLife.00778.014