Activation of MCs in the presence of imDCs leads to increased MC–DC interactions. (A) Typical interaction between either resting (top row) or activated (bottom row) BMMCs and imDCs. (top row) Movements of two separate unactivated BMMCs (represented by either asterisks or plus signs) are tracked along a DC. (bottom row) ActMCs can maintain contact with imDCs for extended periods and demonstrate polarized accumulation of IgE (AF488, green). (B) Duration of MC–DC interactions observed in Video 1 (unactivated, 27 contacts) and Video 2 (activated, 9 contacts). (C) Cartoon demonstrating the single-cell adhesion measurement setup where MCs are first attached to a tipless AFM cantilever then brought into contact with the imDC. (D) Single representative force–distance (F–D) curves of the interaction of an unactivated versus activated MC (MC/9) interacting with an imDC out of five independent experiments. In total, n > 21 MC–DC contacts and n > 120 F–D curves per condition were measured. From these single curves, the work (area under the curve) and Fmax (maximum force to baseline) are quantified. (E) The force in nanonewtons needed to detach unactivated or activated MC/9 MCs from imDCs (unactivated: n = 21 DC–MC contacts in five experiments; activated: n = 43 DC–MC contacts in six experiments) or mouse embryonic fibroblasts (MEF; unactivated: n = 19 DC–MC contacts in two experiments; activated: n = 20 contacts in two experiments). ***, P < 0.001 (by Mann–Whitney test). Values are means ± SEM.
