Activation of human phagocytes by Helicobacter pylori. A novel interaction with neutrophils and monocytes distinct from that of N-formylated oligopeptides.

Sonicate proteins from Helicobacter pylori activate human neutrophils and monocytes for chemotactic and oxidative burst responses. The molecular nature of this activity and its interaction with the phagocyte membrane is unknown. Cross-stimulation experiments were performed with human neutrophils and monocytes preincubated in H. pylori sonicate and subsequently stimulated with the established and characterised stimuli N-f-methionyl-leucyl-phenylalanine (fMLP), the complement split product C5a (in zymosan-activated serum, ZAS), and phorbol-myristate-acetate (PMA). Checkerboard experiments confirmed the sonicate to be truly chemotactic, whereas no chemokinetic activity was demonstrated. At high concentrations of sonicate (1 mg/ml), a depressed chemotactic and oxidative burst response was observed, whereas the viability was > 98%. At lower concentrations (0.01-0.1 mg/ml), only weak deactivation could be induced for monocytes, i.e. the cells had a normal function. With neutrophils, even low concentrations of sonicate depressed the oxidative burs responsiveness. However, the reduced activity was unrelated to the stimulus applied indicating that H. pylori protein(s) activate human neutrophils and monocytes by a membrane binding site distinct from that of previously described receptors.