An apparatus and method for identifying and screening for agents affecting the leukocyte adhesion cascade (LAC) encompassing rolling, adhesion and migration comprises an optically clear, plastic microfluidic chip comprising flow channels with diameters in the range of 10-500 μm. The flow channels are coated with endothelial cells and at least a portion of the flow channels contains 1-30 μm sized openings, optionally filled with a native or synthetic extracellular matrix, that allow leukocyte migration into one or more tissue spaces.