Neutrophil and monocyte adherence to and migration across monolayers of cytokine-activated endothelial cells: the contribution of CD18, ELAM-1, and VLA-4

Abstract

Pretreatment of endothelial cells with cytokines enhances the adherence of leukocytes, a process that is mediated by surface proteins expressed on both cell types. A three-dimensional model system for the simultaneous determination of leukocyte adherence and migration was used to study the contribution of CD11/CD18, endothelial leukocyte- adhesion molecule-1 (ELAM-1) and VLA-4 in neutrophil and monocyte adherence to and migration through cytokine-activated endothelial cells. Pretreatment of endothelial cells for 4 hours with recombinant interleukin-1 beta (rIL-1 beta) was found to enhance neutrophil adherence and migration to a much greater extent than monocyte adherence and migration. Neutrophil adherence was almost completely prevented by the combined use of monoclonal antibodies (MoAbs) against ELAM-1 and CD18. Although ELAM-1 has been designated an endothelial cell-specific cytokine-inducible receptor for neutrophils, we observed that ENA2, an anti-ELAM-1 MoAb, significantly reduced monocyte adherence about 30%. MoAbs against VLA-4, the ligand of the cytokine- inducible receptor VCAM-1, did not affect monocyte adherence. However, the combined use of the MoAbs against CD18, ELAM-1, and VLA-4 had a very strong and additive inhibitory effect on rIL-1 beta-induced monocyte adherence. The anti-CD18 MoAb reduced both rIL-1 beta-induced neutrophil and monocyte migration far below the level of the unstimulated controls, whereas neither the anti-ELAM-1 nor the anti-VLA- 4 MoAb significantly affected the process of migration. Our results indicate that neutrophils and monocytes initially adhere to cytokine- activated endothelial cells by CD18-independent and (to a lesser extent) by CD18-dependent mechanisms and subsequently change gears to a completely CD18-dependent migratory mechanism.

Monocyte‐endothelial cell interactions in vitro, with reference to the influence of interleukin‐1 and tumor necrosis factor

“…Furthermore, in contrast to ELAM-I, which modulates both neutrophil and Mo to cytokine-induced ECs, VCAM functions as a ligand for the integrin VLA-4, which is expressed on monocytes but not on neutrophils. Together with these studies, we found that mAbs against VCAM can inhibit Mo adherence to cytokine-induced ECs by up to 40070, whereas other studies showed that ELAM-I mAb can block this process by 30% [19]. Further quantitative blocking studies with respective antibody against molecules on Mos are needed to evaluate tile precise molecule(s) involved in Mo adhesion.…”

“…The functional differences between Mos and other leukocytes might also be due to the differences of surface characteristics [40]. The molecular basis for Mo active movement on and adhesion to 'resting' ECs is not clear, but a likely candidate would be the leukocyte/32 integrin CDI I / C D I 8 complex because CDI I / C D I 8 is largely required for Mo transendothelial migration [19]. Mo-EC interactions can be regulated by a numbe," of factors [4,10,11,30,42,48], among which IL-I and TNF are notorious for their various originality and plurifunction as inflammatory mediators [24].…”

“…Accumulating evidence suggests that cytokines act on the EC by modulating the expression of surface adhesion molecules and production of monocyte chemoattractants thus promoting Mo-EC interactions [4,11,19,32] although it is still controversial whether these cytokines are indeed chemoattractive for leukocytes [14,27,35,36,45,50,52]. To date, in vitro studies of the mechanisms involved in the Mo-EC interactions have focused on the role of adhesion molecules [2,8,21] and mediators [10,30,42,48].…”

Antibodies to proteinase 3 mediate expression of vascular cell adhesion molecule-1 (VCAM-1)

“…Secondary adhesion molecules belonging to the 1 and 2 integrin families achieve a strong attachment and extravasation of leucocytes [3,30]. VCAM-1 and its ligand VLA-4 play an important role in the in vitro adherence of monocytes and activated T cells [31,32] to endothelium. A recent report [33] that interactions between adhesion molecules like VCAM-1 on HEC may play an important role in the perpetuation of vasculitis.…”

The linoleic acid metabolite 13‐HODE modulates degranulation of human polymorphonuclear leukocytes

“…Expression of CDI l b on the cell surface is not only indicative for PMN degranulation, but also subserves PMN adhesion to other cells. CDll b belongs to the integrin family of adhesion molecules and is involved in the adherence of PMNs to activated endothelial and epithelial cells by interaction with its counterstructure ICAM-I present on these cells [31,32]. Following adhesion, PMNs transmigrate between the cells and migrate ahmg a gradient of chemoattractant, such as PAF and fMLP.…”