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Pathology ` PATHOLOGY—InfLAMMATIOn Pathology ` PATHOLOGY—InfLAMMATIOn SECtIoN II 215

Leukocyte Extravasation predominantly occurs at postcapillary venules.
extravasation
STeP VASCuLATure/STrOMA LeuKOCYTe
Margination and rolling— E-selectin (upregulated by TNF and Sialyl Lewis X
defective in leukocyte adhesion IL-1)
deficiency type 2 ( Sialyl P-selectin (released from Weibel- Sialyl Lewis X
X
Lewis ) Palade bodies)
GlyCAM-1, CD34 L-selectin
Tight binding (adhesion)— ICAM-1 (CD54) CD11/18 integrins
defective in leukocyte adhesion (LFA-1, Mac-1)
deficiency type 1 ( CD18 VCAM-1 (CD106) VLA-4 integrin
integrin subunit)
Diapedesis (transmigration)— PECAM-1 (CD31) PECAM-1 (CD31)
WBC travels between
endothelial cells and exits blood
vessel

Migration—WBC travels Chemotactic factors: C5a, IL-8, Various
through interstitium to site of LTB 4 , kallikrein, platelet-activating
injury or infection guided by factor
chemotactic signals

Margination & rolling 2. Tight binding 3. Diapedesis 4. Migration
Sialyl Lewis X
Vessel PMN
lumen PMN PMN
E-selectin P-selectin LFA-1 PMN PECAM-1
ICAM-1

Endothelium

Interstitium
PMN

PMN

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