Table 1.

Endothelial Cell characteristics at sites of leukocyte transmigration.

Organ: Barrier	EC Type/BM Characteristics	EC : PC ratio	Primary TEM location	Basal LAM expression	Inflammatory LAM expression
Brain: Blood-Brain Barrier	Continuous/BM present	1 : 1 to 3 : 1	Post-capillary venules	• Very low overall • PECAM-1 • ALCAM-1 • ICAM-2 • MHC Class I	• Upregulates P-selectin (not stored in Weibel-Palade bodies), E-selectin • Upregulates ICAM-1, ICAM-2, VCAM-1, ALCAM-1
Lungs: Air-Blood Barrier	Continuous/thin BM	7 : 1 to 9 : 1	Capillaries	• PECAM-1 • ICAM-1, ICAM-2	• Upregulates P-selectin and E-selectin, but not required for rolling • Upregulates ICAM-1, MHC Class II
Lungs: Bronchial Capillary Barrier	Continuous/thin BM	7 : 1 to 9 : 1	Post-capillary venules	• PECAM-1 • E-selectin, P-selectin • ICAM-1, ICAM-2, VCAM-1	• Upregulates P-selectin and E-selectin • Upregulates ICAM-1, VCAM-1
Kidney: Glomerular Capillaries	Fenestrated/BM present	2.5 : 1	Capillaries	• PECAM-1 • ICAM-1, ICAM-2 • Low MHC Class I and II	• Upregulates E-selectin, relies on platelets for P-selectin, rolling under debate • Upregulates ICAM-1, VCAM-1, MHC Class I and II
Liver: Liver Sinusoids	Discontinuous/no organized BM	10 : 1	Capillaries, some at post-capillary venules	• JAM-A • ICAM-1, ICAM-2, VAP-1 • MHC Class I and II	• Does not require selectins but subset can upregulate E-selectin • Upregulates ICAM-1, VCAM-1, VAP-1, MHC Class II

EC, endothelial cell; BM, basement membrane; PC, pericyte; TEM, transmigration; LAM, leukocyte adhesion molecule; PECAM-1, platelet endothelial cell adhesion molecule-1; ALCAM-1, activated leukocyte cell adhesion molecule-1; ICAM-1, intercellular adhesion molecule-1; ICAM-2, intercellular adhesion molecule-2; VCAM-1, vascular cell adhesion molecule-1; MHC, major histocompatibility complex; JAM-A, junctional adhesion molecule-A; VAP-1, vascular adhesion protein-1.