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Biosynthesis of the third and fifth complement components by isolated human lung cells.
B L Rothman1, M Merrow, M Bamba
1Department of Pathology, University of Connecticut Health Center, Farmington 06032.
The American Review of Respiratory Disease
|January 1, 1989
Summary
Lung cells, including pneumocytes and fibroblasts, synthesize key complement proteins involved in host defense and inflammation. This cell-derived complement plays a crucial role in regulating lung inflammatory responses.
Area of Science:
- Immunology
- Cell Biology
- Pulmonary Medicine
Background:
- Complement system locally synthesized components are critical for host defense and inflammation.
- Understanding cell-derived complement production in lung tissue is essential for comprehending inflammatory processes.
Purpose of the Study:
- To determine the capacity of lung pneumocytes (A549) and fibroblasts (WI-38) to synthesize complement components in vitro.
- To quantify the production of C3 and C5 by these lung cells.
Main Methods:
- Biosynthesis of complement proteins demonstrated via [35S]methionine incorporation and immunoprecipitation.
- Enzyme-linked immunospecific assays used to quantify C3 and C5 production.
- Comparison of complement production under serum-containing and serum-free conditions.
Main Results:
- A549 pneumocytes synthesize a broad range of complement components, including C3, C5, C4, C6-C9, Factor B, H, I, and C1s inactivator.
- WI-38 fibroblasts synthesize a subset of complement components, including C3, C5, C4, C6, C8, and C9.
- Fetal bovine serum (FBS) significantly enhances C3 and C5 production by A549 cells.
Conclusions:
- Lung pneumocytes and fibroblasts are significant sources of locally synthesized complement proteins.
- Cell-derived complement, particularly C3 and C5, contributes to lung inflammation and injury.
- Serum factors influence the rate of complement component production by lung cells.