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Vitronectin stabilizes leukocyte adhesion
WT recipient mice. Thus, a neutrophil-intrinsic effect of VN deficiency was not evident.
Role of integrin interaction partners of vitronectin for neutrophil trafficking
Platelets are known to play a critical role in the extrava- sation process of leukocytes.11-14 Since αvb3 and αIIbb3
A
integrins are expressed on the surface of platelets and serve as binding partners of VN, this glycoprotein might stabilize intravascular adhesion of neutrophils by mediating interac- tions of these cell populations. Using in vivo microscopy on the postischemic mouse cremaster muscle, however, intravascular firm adherence of platelets or interactions of intravascularly adherent platelets and neutrophils did not
B
C
D
Figure 3. Role of platelets and integrins for the stabilization of intravascular adhesion of neutrophils. (A) Interactions of Ly-6G+ neutrophils (red) and GP-Ibb+ platelets (green) were analyzed in postcapillary venules (perfused by FITC dextran; grey) of the postischemic mouse cremaster muscle of wild-type (WT) or vitronectin (VN)-defi- cient mice by multi-channel in vivo microscopy, representative images from a WT mouse are shown (scale bar: 10 mm). Panels show quantitative results for intravas- cular adherence of neutrophils or platelets as well as for the colocalization of these two cell populations (mean±standard error of the mean [SEM] for n=3 animals per group; *P<0.05 vs. WT). Further panels show quantitative results for rolling flux, rolling velocity, short adhesion, firm adherence, adhesion time, and transmigration of neutrophils in WT mice receiving platelet-depleting antibodies, blocking antibodies directed against the b2 integrins LFA-1/CD11a and Mac-1/CD11b (B), or ICAM- 1/CD54 (C), or blocking antibodies directed against CD51 integrins and αIIbb3/CD41/CD61 integrins (D; mean±SEM for n=4 animals per group; *P<0.05 vs. isotype control). See also Online Supplementary Table S1. n: numbers, s: seconds; min: minutes; I/R: ischemia-reperfusion; mAb: monoclonal antibody.
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