Schematic diagrams illustrating potential pathways involved in leukocyte/vessel wall interactions. (A) The potential roles of leukocyte and EC TNF-α receptors in mediating leukocyte/vessel wall interactions. The diagrams are based on our findings and published works. (B) The EC molecules ICAM-2, JAM-A, and PECAM-1 act sequentially to mediate leukocyte transmigration through venular walls in vivo. ICAM-2 acts at an early stage where leukocytes are thought to be “investigating” an EC junction, JAM-A mediates migration through EC junctions, and PECAM-1 supports migration through the vascular BM.