| Popis: |
Nonopsonized Bordetella pertussis, the causative agent of whooping cough, can attach to and become ingested by human monocytes. It has been reported that complement receptor type 3 (CR3) on human monocyte-derived macrophages binds filamentous hemagglutinin expressed on B. pertussis. In the present study, the role of very late antigen-5 (VLA-5) in the attachment of B. pertussis to adherent human monocytes was investigated. It was found that soluble fibronectin and soluble mAb against VLA-5 markedly inhibited the attachment of B. pertussis to monocytes. When VLA-5 on monocytes was cross-linked by plating these cells onto surfaces precoated with fibronectin or mAb against VLA-5, the binding of both B. pertussis and C3bi-coated sheep erythrocytes to these cells was significantly enhanced, whereas the binding of a B. pertussis mutant strain deficient in filamentous hemagglutinin was not affected. The enhanced attachment of B. pertussis to monocytes plated onto fibronectin-coated surfaces was markedly inhibited by soluble mAb against CR3. Neutrophils, which express similar levels of CR3 and about 10-fold lower levels of VLA-5 as compared with monocytes, did not bind B. pertussis. Together, these results indicate that VLA-5 is involved in the attachment of B. pertussis to monocytes and that cross-linking of VLA-5 enhances the attachment of B. pertussis to monocytes by augmenting the binding activity of CR3. We propose that the attachment of B. pertussis to monocytes occurs in two steps: binding and cross-linking of VLA-5 by B. pertussis enhances the binding activity of CR3, which in turn facilitates the subsequent binding of these bacteria to the latter receptor. |
