Figure 3.

The effects of integrin engagement are distributed across the actin network. Jurkat T cells were allowed to interact with mixed-mobility surfaces bearing patterns of immobilized VCAM-1, surrounded by planar bilayers coated with anti-CD3 and imaged for 4 min. Pattern (A) has 1 µm diameter spots with center-to-center distance of 3 µm. Patterns (B,C) have 2 µm diameter spots with center-to-center distances of 4 and 5 µm, respectively. (D) Actin flow rates were assessed within the lamellipodial region, choosing areas that overlie the immobile spots (on pattern, yellow dashed lines) or bypass them completely (off pattern, blue dashed lines). The red dashed line marks the actin flow on bilayers coated with anti-CD3. (E) Jurkat T cells were allowed to interact with surfaces patterned with bars of immobilized VCAM-1 (1 µm wide, 5 µm center-to-center), surrounded by planar bilayers coated with anti-CD3 and imaged for 4 min. (F) Actin flow rates were assessed within the lamellipodial region, choosing areas overlying the immobile bars (on pattern, yellow dashed lines), bypass them completely (off pattern, blue dashed lines) or where the free edge of the lamellipodium lies between bars (outside pattern, white dashed line). The red dashed line marks actin flow for cells spread on bilayers coated with anti-CD3. (G) Measurements of actin velocity were made parallel to the bars in the space between two bars. Mean ± SD is calculated for measurements made in 20–40 cells for each condition, *p < 0.05, ***p < 0.001. Scale bars = 10 µm.