BORDETELLA-PERTUSSIS FILAMENTOUS HEMAGGLUTININ INTERACTS WITH A LEUKOCYTE SIGNAL-TRANSDUCTION COMPLEX AND STIMULATES BACTERIAL ADHERENCE TOMONOCYTE CR3 (CD11B CD18)/

Bordetella pertussis, the causative agent of whooping cough, adheres t o human monocytes/macrophages by means of a bacterial surface-associat ed protein, filamentous hemagglutinin (FHA) and the leukocyte integrin , complement receptor 3 (CR3, alpha(M) beta(2), CD11b/CD18), We show t hat an FHA Arg-Gly-Asp site induces enhanced B. pertussis binding to m onocytes, and that this enhancement is blocked by antibodies directed against CR3. Enhancement requires a monocyte signal transduction compl ex, composed of leukocyte response integrin (alpha(?)beta(3)) and inte grin-associated protein (CD47). This complex is known to upregulate CR 3 binding activity. Thus, a bacterial pathogen enhances its own attach ment to host cells by coopting a host cell signaling pathway.