Figure 1

(a) Three subsequent positions of the model immune cell (white circles), which is equipped with a central concentration sensor for temporal gradient sensing (black dot) and two lateral concentration sensors for spatial gradient sensing (orange dots). The magnitude of the turning angle |Δϕ_c,n| can be applied with negative of positive sign (blue). (b) Stationary radial profile of chemo-attractant density f_2D(r) around a non-moving emitter, for different diffusion lengths l_dif. The semi-logarithmic inset shows that the profile decays almost exponentially for large radial distances r → ∞. (c) Distribution of the number of targets encountered by the immune cell over 10⁵ simulation runs. The three shown cases correspond to the standard parameters (SP, blue), to standard parameters with the immune cell persistence increased to ε_N = 1 (olive), and to standard parameters with both ε_N = 1 and speed increased to v_N = 6 μm/min (red). (d) Example configuration of static targets (orange dots), concentration distribution of the guiding substance (color code), and the trajectory of the immune cell (small gray dots) over 500 min. The immune cell is set to standard parameters (c_A0 = −5, c_A1 = c_R1 = 0, v_N = v_A = 3, and ε_N = ε_A = 0.5).