MT1-MMP is enriched at the leading edge of monocytes migrating on activated endothelial cells. (A) MT1-MMP (green) and CD45 (red) were stained in fresh monocytes adhered for 2 hours in the presence of 100 ng/mL MCP-1 to endothelial cells previously stimulated with 20 ng/mL TNF-α for 12 hours. Selected confocal sections and the merged overlay of all sections are presented. Arrowheads indicate areas where MT1-MMP and CD45 colocalize at monocyte membrane ruffles. (B) MT1-MMP (green) and profilin (red) were stained in fresh monocytes adhered for 2 hours in the presence of 100 ng/mL MCP-1 to endothelial cells previously stimulated with 20 ng/mL TNF-α for 12 hours. Selected confocal sections and the merged overlay of all sections are presented. Arrowheads indicate areas where MT1-MMP and profilin colocalize at monocyte leading edge.