Antimyeloperoxidase autoantibodies are found in the sera of some patients with glomerulonephritis and systemic vasculitis. Previously, we demonstrated that they were able to stimulate neutrophils to damage cultured human endothelial cells. We now report that antimyeloperoxidase antibodies are able to stimulate neutrophils to adhere to cultured human endothelial cells. Immunoglobulin G purified from myeloperoxidase-antineutrophil cytoplasmic autoantibody positive sera increased adherence to 331 +/- 60% of unstimulated controls. In a similar manner, rabbit antimyeloperoxidase enhanced neutrophil adherence. Stimulating the endothelial cells with 10 micrograms/mL endotoxin enhanced antimyeloperoxidase stimulated adherence. In the presence of a CD18 blocking antibody (MoAb 60.3), antimyeloperoxidase-stimulated adherence was significantly decreased. These results add further understanding to the antimyeloperoxidase-stimulated neutrophil-endothelial cell interaction and further support the hypothesis that antimyeloperoxidase autoantibodies are of pathogenic import in glomerulonephritis and vasculitis.