Stimulation of eosinophil adherence to human vascular endothelial cells in vitro by platelet-activating factor.
111In-Labeled eosinophils from mildly eosinophilic subjects have been examined for their capacity to adhere to cultured human umbilical vein endothelial cells. In assay buffer alone, 32.0% +/- 2.6 eosinophils adhered spontaneously to endothelial cells. Platelet-activating factor (PAF) (1-alkyl-2-acetyl-sn-glycero-3-phosphorylcholine) at concentrations as low as 10(-9) M increased this adherence to a level of 46.7% +/- 2.0. The effects of PAF were confirmed to be on eosinophils by parallel adherence assays done on serum-coated plastic plates where comparably enhanced adhesion of the eosinophils was seen. Lyso-PAF, the biologically inactive precursor/metabolite of PAF, had no stimulatory properties. FMLP caused an increase in eosinophil adherence, comparable to that of PAF, but only at high concentrations (10(-6) to 10(-7) M). Further examination of eosinophil subpopulations separated on metrizamide gradients indicated that "hypodense" eosinophils had a significantly higher ability to adhere spontaneously to endothelial cells than "normal" dense eosinophils, (35.5% +/- 4.2 vs 23.8% +/- 2.5, respectively) and could be stimulated with PAF to higher levels, although the magnitude of stimulation was similar for both populations. A mouse mAb TS1/18 to the common beta-subunit of the Mac-1 cell surface glycoprotein complex (CDw18) reduced by up to 94.6% the PAF-induced increase in adherence, but had no effect on the spontaneous adhesion. Eosinophils were also shown by cytofluorography to be capable of binding the TS1/18 antibody on their cell surface, and in some experiments to exhibit an increased expression of the Mac-1 complex on stimulation with PAF. These studies indicate that eosinophils are capable of binding to endothelial cells in culture, that PAF is a potent stimulator of eosinophil adherence, and that the Mac-1 complex has a critical role in this adhesion process.
Kimani
G
G
Department of Pediatrics, National Jewish Center for Immunology and Respiratory Medicine, Denver, CO 80206.
Tonnesen
M G
MG
Henson
P M
PM
D000911:Antibodies, Monoclonal / Q000276:immunology; D000943:Antigens, Differentiation / Q000502:physiology; D000954:Antigens, Surface / Q000502:physiology; D002448:Cell Adhesion / Q000187:drug effects*; D015815:Cell Adhesion Molecules; D004730:Endothelium, Vascular / Q000166:cytology*; D004804:Eosinophils / Q000145:classification / Q000166:cytology*; D005434:Flow Cytometry; D006801:Humans; D066298:In Vitro Techniques; D009240:N-Formylmethionine Leucyl-Phenylalanine / Q000494:pharmacology; D010972:Platelet Activating Factor / Q000494:pharmacology*
D000911:Antibodies, Monoclonal; D000943:Antigens, Differentiation; D000954:Antigens, Surface; D015815:Cell Adhesion Molecules; D010972:Platelet Activating Factor; D009240:N-Formylmethionine Leucyl-Phenylalanine