Abstract
We introduce quantitative dynamic footprinting microscopy to resolve neutrophil rolling on P-selectin. We observed that the footprint of a rolling neutrophil was fourfold larger than previously thought, and that P-selectin-PSGL-1 bonds were relaxed at the leading edge of the rolling cell, compressed under the cell center, and stretched at the trailing edge. Each rolling neutrophil formed three to four long tethers that extended up to 16 μm behind the rolling cell.