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Serum regulates the expression of complement receptor 2 on human B cell lines
1Department of Cellular Injury, Walter Reed Army Institute of Research, Washington, DC 20307-5100, USA. mtolnay@hotmail.com
Immunopharmacology and Immunotoxicology
|August 22, 2000
Summary
Serum factors significantly increase complement receptor 2 (CR2) expression on B cells, impacting immune responses. Interferon-gamma and specific antibodies can block this serum-induced CR2 gene upregulation.
Area of Science:
- Immunology
- Molecular Biology
- Cell Biology
Background:
- Complement receptor 2 (CR2) is crucial for regulating B cell responses to antigens.
- CR2 interacts with C3d complexes, influencing B cell activation thresholds.
Purpose of the Study:
- To investigate the effect of serum factors on CR2 gene and protein expression in B cells.
- To identify regulatory mechanisms influencing CR2 expression, including cytokines and antibodies.
Main Methods:
- Treatment of B lymphoblastoid (IM-9) and Burkitt's lymphoma (Raji) cells with heat-inactivated fetal bovine serum.
- Quantitative analysis of CR2 and CD19 mRNA levels using RT-PCR.
- Assessment of CR2 surface protein expression via flow cytometry.
- Investigation of cytokine and monoclonal antibody effects on CR2 expression.
Main Results:
- Serum treatment for 24 hours increased CR2 mRNA and surface protein expression over two-fold in B cells.
- CD19 mRNA levels decreased independently of serum presence.
- Interferon-gamma (IFN-γ) and the CR2-specific antibody OKB7 inhibited the serum-induced increase in CR2 mRNA levels.
- Serum-induced CR2 upregulation was not linked to changes in cell proliferation or mimicked by other cytokines.
Conclusions:
- Serum contains factors that directly induce CR2 gene expression in B cells.
- IFN-γ and OKB7 signaling pathways interfere with serum-mediated CR2 upregulation.
- Serum-derived factors may play a significant role in modulating B cell responsiveness to complement-tagged antigens.