Complement levels and activity in the normal and LPS-injured lung.


Journal Article

Complement, a complex protein system, plays an essential role in host defense through bacterial lysis, stimulation of phagocytosis, recruitment of immune cells to infected tissue, and promotion of the inflammatory response. Although complement is most well-characterized in serum, complement activity is also present in the lung. Here we further characterize the complement system in the normal and inflamed lung. By Western blot, C5, C6, and factor I were detected in bronchoalveolar lavage (BAL) at lower levels than in serum, whereas C2 was detected at similar levels in BAL and serum. C4 binding protein (C4BP) was not detectable in BAL. Exposure to lipopolysaccharide (LPS) elevated levels of C1q, factor B, C2, C4, C5, C6, and C3 in human BAL and C3, C5, and factor B in mouse and rat BAL. Message for C1q-B, C1r, C1s, C2, C4, C3, C5, C6, factor B, and factor H, but not C9 or C4BP, was readily detectable by RT-PCR in normal mouse lung. Exposure to LPS enhanced factor B expression, decreased C5 expression, and did not affect C1q-B expression in mouse and rat lung. BAL from rats exposed to LPS had a greater ability to deposit C3b onto bacteria through complement activation than did BAL from control rats. In summary, these data demonstrate that complement levels, expression, and function are altered in acute lung injury and suggest that complement within the lung is regulated to promote opsonization of pathogens and limit potentially harmful inflammation.

Full Text

Cited Authors

  • Bolger, MS; Ross, DS; Jiang, H; Frank, MM; Ghio, AJ; Schwartz, DA; Wright, JR

Published Date

  • March 2007

Published In

Volume / Issue

  • 292 / 3

Start / End Page

  • L748 - L759

PubMed ID

  • 17071722

Pubmed Central ID

  • 17071722

International Standard Serial Number (ISSN)

  • 1040-0605

Digital Object Identifier (DOI)

  • 10.1152/ajplung.00127.2006


  • eng

Conference Location

  • United States