Adhesion Molecules in Decompression Sickness and Ischemia Reperfusion Injury - Adhesion Molecules - page 167

monocytes/macrophages into tissue sites. h e expression of ligands for these
molecules (Tables 1, 2) (Rahman and Fazal 2009) helps to determine sites of
adhesion followed by extravasation. h e choice of a paracellular versus transcellular
leukocyte migration pathway depends upon the tightness of the intercellular
junctions of the endothelial cells, the type of stimuli, the type of leukocytes and
the endothelial cell source. Rahman and Fazal note that transcellular leukocyte
migration appears to occur more prominently in vascular areas where endothelial
junctions are particularly tight, such as the blood-brain barrier, while paracellular
migration of leukocytes occurs in vascular areas in which the endothelial junctions
are less tight, such as postcapillary venules. Activation of endothelium may result
from release of inl ammatory cytokines (IL-1, TNF-α, IL-6) by endothelial cells
and/or monocytes/macrophages following endothelial injury during reperfusion
or by the gas bubbles causing DCS (Table 3) . In the development of DCS, the
surface of nitrogen bubbles that appear in the blood, extracellular space, and
intracellular space during decompression may trigger an inl ammation and
activation of a cytokine cascade (Ersson et al. 1998, 2002) that increases ICAM-1/
VCAM-1 expression.
Key Points Endothelium is activated by inl ammatory molecules called
cytokines. Blood leukocytes expressing certain CAMs interact with endothelial
co-ligands, which permits transmigration of blood leukocytes into the injured
tissue site.

Table 1 Cell adhesion molecule pairs on endothelia and blood mononuclear cells

CAM (immunoglubulin superfamily structure) Ligand (integrins α 2 β 1 )
ICAM-1; ICAM-2 LFA-1
VCAM-1 VLA-4
h is information describes the CAMs found increased on endothelia and their corresponding co-
ligands.

Table 2 Distribution of cell adhesion molecules involved in transmigration of blood
leukocytes through injured/inflamed endothelia

ICAM-1 Activated endothelia, lymphocytes, dendritic cells

ICAM-2 Resting endothelia, lymphocytes, dendritic cells

VCAM-1 Activated endothelia

LFA-1 Monocytes, macrophages, T lymphocytes, neutrophils, dendritic cells

VLA-4 Monocytes, macrophages, lymphocytes