Antineutrophil cytoplasmic antibodies stabilize adhesion and promote migration of flowing neutrophils on endothelial cells

Objective. Recruitment of neutrophils to sites of inflammation requires coo rdinated regulation of their capture, activation, and migration on vascular endothelium. This study examines whether exposure of neutrophils to antine utrophil cytoplasmic antibodies (ANCAs) can disrupt this sequence of events . Methods. Isolated human neutrophils were perfused in the presence or absenc e of ANCA-positive IgG over endothelial cells that had been activated with either 2 units/ml or 100 units/ml of tumor necrosis factor a (TNF alpha) fo r 4 hours. Results. When endothelial cells were activated with 100 units/ml of TNF alp ha, neutrophils were captured from flow, a small proportion of adherent cel ls rolled, and the majority transmigrated through the endothelial cell mono layer. When neutrophils were treated with ANCA IgG immediately before, 5 mi nutes before, or 15 minutes before perfusion, none rolled on contact with t he endothelium, but the majority still transmigrated. When endothelial cell s were activated with 2 units/ml of TNF alpha, the majority of untreated ad herent neutrophils rolled, a few transmigrated, and the number that attache d decreased with time during washout. In contrast, when neutrophils were pr etreated with ANCA IgG just before perfusion, adhesion was stabilized, and the number of neutrophils that transmigrated was increased 10-fold. Priming of the neutrophils with TNF alpha before the addition of ANCA further incr eased the stability of neutrophil binding, but did not significantly increa se transmigration. Conclusion. Rather than frustrating the transmigration process, ANCAs promo ted the migration of neutrophils through the endothelium. That the effect w as evident at a relatively low level of endothelial activation suggests tha t ANCAs may potentiate the early vasculitic lesion and promote tissue damag e and recruitment of other proinflammatory cells.