Involvement of the beta(2)-integrin CD18 in apoptosis signal transduction in human neutrophils

Objective and design: To examine the hypothesis that an accelerated rate of neutrophil apoptosis occurs following beta(2)-integrin activation, and fur ther investigate the signal transduction pathways involved. Material: Human polymorphonuclear neutrophils. Treatment: Neutrophils were challenged with pansorbins coated with antibodi es towards the beta(2)-integrin subunit CD18 in a proportion of 1:100 with or without the inhibitors diphenylene iodonium (10 M), cytochalasin B (5 mu g/ml), genistein (10 nM), herbimycin A (10 M) and Z-VAD-FMK (10 mu M). Methods. Measurement of phosphatidylserine exposure and DNA fragmentation i n flow cytometry and assessment of H2O2-production through spectrofluoromet ry. The results were analysed using Mann Whitney U test and Kruskal Wallis. Results: Pansorbins coated with antibodies to CD18 induce apoptosis in neut rophils (p < 0.01), and activate the production of reactive oxygen species (p < 0.01). Pre-treatment with the inhibitors have no effect on anti-CD18 i nduced apoptosis. Conclusion: Anti-CD18 pansorbins induce apoptosis in neutrophils through an alternative pathway not involving reactive oxygen species and independent of tyrosine phosphorylation, cytoskeletal reorganisation and caspases.