Fig. 1.

Effects of mechanical force on early stages of T cell activation. (A) Schematic of initial TCR–pMHC interaction between T cell and APC. (B) Illustration of the force dependence of $k_{\text{off}}$ for a slip and a catch bond. (C–J) Number of total TCR phosphorylation $N_p$ as a function of external average force $f_0$ in absence (C) and in presence of force fluctuations (D and H), force frequency $\omega$ (E and I), and rebinding rate $k_{\text{reb}}$ (F, G, and J). Parameter values (if not varied): $f_c=25$ pN, $f_{\omega }=5$ pN, $\omega =0$ s⁻¹, $a/k_{B}T=1$ pN⁻¹, and $k_{\text{off,0}}=k_p=1$ $s^{-1}$.