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The Bb fragment of complement factor B acts as a B cell growth factor
M G Peters1, J L Ambrus, A S Fauci
1Department of Medicine, Washington University School of Medicine, St. Louis, Missouri 63110.
The Journal of Experimental Medicine
|October 1, 1988
Summary
The complement component Bb enhances B cell proliferation and differentiation, acting as an early immune response signal at inflammatory sites. This finding reveals a novel role for Bb in amplifying immune responses.
Area of Science:
- Immunology
- Complement System
- B cell Biology
Background:
- B cell differentiation into plasma cells is a regulated process influenced by inflammatory mediators.
- The complement system, particularly Factor B cleavage products, may play a role in immune regulation.
Purpose of the Study:
- To investigate the regulatory influence of Bb, a complement Factor B peptide, on human B cell proliferation and differentiation.
- To explore the relationship between Bb and the B cell growth factor HMW-BCGF.
Main Methods:
- Human splenic and tonsillar B cells were cultured with purified Bb, Staphylococcus aureus Cowan I (SAC), and/or HMW-BCGF.
- Proliferation was assessed in a dose-dependent manner.
- Antigenic relationships were studied using antibodies, and Bb binding to B cells was measured.
Main Results:
- Bb alone had no effect on B cell proliferation, but enhanced it when B cells were activated by SAC.
- Bb potentiated proliferation with suboptimal HMW-BCGF but not with optimal concentrations.
- Bb demonstrated antigenic and functional similarities to HMW-BCGF, binding to activated B cells.
Conclusions:
- Bb acts as a B cell growth and differentiation factor at potentially physiologic concentrations.
- Bb may serve as an early inflammatory signal for clonal expansion of antigen-activated B cells.
- Bb's role in amplifying immune responses at inflammatory sites is suggested.