Fig. 4.

Why the TCR can be triggered in the absence of ligands. (A) Probability that a TCR remains inside a close contact for time, τ, for close contacts of varying fixed radius, r₀. (B) Probability that a single TCR stays inside a close contact >2 s as a function of final close-contact radius for growing contacts. (C) Total number of TCRs that remain inside the close contact for >2 s, incorporating the estimates shown in A, the density of TCRs in Jurkat T cells, and the degree of exclusion of the TCR from close contacts for cells interacting with rCD2-presenting SLBs. (D) Total contact area (region of CD45 exclusion) at the time of calcium release for T cells interacting with rCD2-presenting SLBs (13 cells, 5 independent experiments). Central lines indicate the median; small squares indicate the mean; boxes show interquartile range; whiskers indicate SD.