Tissue Development, Repair, and Remodeling - Tissue Functioning and Remodeling in the Circulatory and Ventilatory Systems - page 704

Table 11.7. Adhesion molecules of leukocyte binding to endothelium and their interactions
and functions (Source: [ 1448 ]; HCAM: homing cell adhesion molecule; I: integrin; TEM:
transendothelial migration). High endothelial venules (HEV) are specialized postcapillary venous
swellings with cuboidal endothelial cells in all secondary lymphoid organs, except the spleen,
that enable circulating leukocytes to enter lymph nodes in any organ, tonsils and adenoids in
the pharynx, Peyer's patches in the small intestine, and small aggregates of lymphoid tissue in
the stomach and large intestine, once they have crossed high endothelial venules. Sialyl Lewis
antigen X (sLe x ), a carbohydrate E-selectin ligand, is constitutively expressed on granulocytes and
monocytes; it mediates their extravasation. It is also expressed by activated T (e.g., T H1 , but not
T H2 cells) and B lymphocytes.

Neutrophil Endothelial cell Role

Receptor Receptor

Selectin L-selectin, E/P-selectins Rolling,

sLe x

interactions GAGCAM, binding to HEV

neutrophil
addressins

Integrin-IgCAM α L β 2 -I ICAM1/2, Adhesion;

α 4 β 1 -I

interactions VCAM1 homing

IgCAM PECAM1 PECAM1 Adhesion potentiation;

interactions HCAM TEM;

binding to connective
tissue components

Immunoglobulin-like Adhesion Molecules

Several integrin ligands, such as vascular cell (VCAM1) and intercellular (ICAM1-
ICAM2) adhesion molecules, are involved in firm adhesion, crawling, and para-
cellular and transcellular migration. Other types of Ig-like adhesion molecules,
such as platelet-endothelial cell (PECAM1), junctional (JAM), and endothelial cell-
selective adhesion molecule (ESAM), T-cell surface glycoprotein-E2 (or CD99),
among others, act during paracellular transmigration [ 1445 ](Table 11.8 ).
Receptor VCAM1 is the endothelial ligand for the

α β α β

1 -and 7 -integrins. 4 4

α β α β

Both ICAM1 and ICAM2 tether 2 -integrins. Mucosal vascular ad-

dressin cell adhesion molecule (MAdCAM) is a major ligand of

2 -and L M

α β

7 -integrin and
L-selectin. Adhesion molecules PECAM1 and JAMs can interact with themselves
as well as with integrins [ 1445 ].

4