The fifth component of complement is not required for the clearance of Staphylococcus aureus.

Both resident alveolar macrophages and recruited polymorphonuclear leukocytes (PMN) are required for pulmonary clearance of large inoculums of Staphylococcus aureus. We have evaluated the role of the C5 molecule in the recruitment of PMN to the lung after challenges with S. aureus using congenic C5-sufficient B10.D2/nSn (C5+) and C5-deficient B10.D2/oSn (C5-) mice. The C5+ and C5- mice were injected with water and varying inoculums of staphylococci via an endobronchial catheter. Bronchoalveolar lavage (BAL) was performed on the inoculated lung at 0 and 4 h after inoculation. Cellular response was measured and chemotactic activity was assayed in BAL supernatants at each time interval using human PMN in modified Boyden chambers by the leading front technique. Clearance of bacteria was studied by quantitative lung culture. The C5+ and C5- mice recruited similar numbers of PMN after challenges with both 10(4), 10(8), and 10(7) organisms (p = NS). The C5+ and C5- mice also generated similar amounts of chemotactic activity in BAL (p = NS). Additionally, clearance of bacteria was not impaired in C5- mice when compared with that in C5+ mice (p = NS). Our results indicate that intraalveolar chemotaxins other than C5 are of primary importance in the early recruitment of PMN after staphylococcal challenge and demonstrate that the inflammatory response within the lung is mediated by differing pathways dependent on the initiating stimulus.