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Expression of properdin in human monocytes
W Schwaeble1, H P Huemer, J Möst
1Department of Immunology, University of Leicester, England.
European Journal of Biochemistry
|February 1, 1994
Summary
Properdin, a key regulator of complement activation, is primarily expressed in monocytes. Its expression and secretion are modulated by various immune signals, linking innate immunity to complement pathways.
Area of Science:
- Immunology
- Complement System Biology
Background:
- Properdin is the sole known positive regulator of the alternative pathway of complement activation.
- Understanding properdin's regulation is crucial for comprehending complement-mediated immune responses.
Purpose of the Study:
- To investigate the cell-specific expression of properdin.
- To elucidate the regulatory mechanisms controlling properdin expression and secretion in monocytes.
Main Methods:
- Northern blot analysis to assess properdin mRNA levels in various cell lines.
- Enzyme-linked immunosorbent assay (ELISA) to measure properdin secretion.
- Treatment of monocytic cells (Mono Mac 6) and primary monocytes with various stimuli (phorbol ester, LPS, cytokines).
Main Results:
- Properdin expression was restricted to myelomonocytic and monocytic cell lines (HL-60, U-937, Mono Mac 6).
- Bacterial lipopolysaccharide (LPS), interleukin-1 beta, and tumor necrosis factor-alpha significantly enhanced properdin mRNA and secretion in Mono Mac 6 cells.
- Recombinant interferon-gamma consistently suppressed properdin mRNA abundance and secretion in both cell lines and primary monocytes.
Conclusions:
- Monocytes are a key source of properdin, a critical regulator of complement.
- Properdin expression and secretion by monocytes are differentially regulated by pro-inflammatory cytokines and bacterial products.
- These findings establish a link between innate immune activation and the alternative complement pathway via monocyte-derived properdin.