Fig. 5. CTL number and collective behavior determine probability of killing.
a Two representative images showing CTL clustering on the spheroid during first fragmentation event. The white circles have a radius of 30 μm around fragmenting cell. b Distribution of the CTL numbers within a radius ≤30 μm around the fragmentation areas (N = 31). c Sketch summarizing the observed trends: CTLs (green) migrate on the surface of the spheroid and cluster together in particular regions, where fragmentation of B16 cells (red) is observed. d During a time-interval Δt, a spheroid with n CTLs attached to it has a probability ΓfragΔt of fragmenting. e Illustration of possible scenarios of the number of CTLs on the spheroids and the apparition of fragmentation. f The fragmentation rate Γfrag can be modeled as the result of independent CTLs interacting with the spheroid, with an individual fragmentation rate per CTL worth ρ. Conversely, the fragmentation rate can be viewed as the result of a collaborative process. g Estimates of Γfrag as a function of the number of CTLs on the spheroid n. Experimental measurements (N = 84, black dots) are fitted with an exponential (dashed red line) compared with the results of the independent CTL model (dashed blue line). Source data are provided as a Source data file.