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CD40-activated surface IgD-positive lymphocytes constitute the long term IL-4-dependent proliferating B cell pool
L Galibert1, I Durand, J Banchereau
1Schering-Plough, Laboratory for Immunological Research, Dardilly, France.
Insights
B cells stimulated with anti-CD40 and IL-4 in vitro lose germinal center features and preferentially proliferate. Long-term proliferating B cells are primarily sIgD-positive, indicating a shift towards non-germinal center characteristics.
Area of Science:
- Immunology
- Cell Biology
- Molecular Biology
Background:
- B cells are crucial for adaptive immunity, with germinal centers (GCs) playing a key role in antibody maturation.
- In vitro culture systems are used to study B cell activation and proliferation.
Purpose of the Study:
- To investigate the characteristics of B cells proliferating in vitro upon CD40 stimulation and IL-4 presence.
- To determine the role of sIgD expression in B cell proliferation and differentiation under these conditions.
Main Methods:
- In vitro culture of B cells with anti-CD40 and IL-4.
- Magnetic cell separation to isolate sIgD+ and sIgD- B cell populations.
- Flow cytometry to analyze sIgD and DNA content.
- Experiments using G8 Id-positive B lymphocytes for population tracking.
Main Results:
- Proliferating B cells lose germinal center features and acquire non-GC markers.
- Both sIgD+ and sIgD- B cells proliferate, with sIgD+ cells showing higher growth rates.
- B lymphocytes maintain sIgD expression during cell cycle progression.
- Long-term proliferating populations are derived from sIgD+/sIgM+ cells, while sIgD-/sIgM- cells are diminished.
Conclusions:
- Anti-CD40 and IL-4 activated B cell blasts exhibit non-GC characteristics.
- sIgD+ B cells preferentially proliferate in the CD40-stimulated system.
- The study discusses the potential in vivo implications of IL-4 and CD40 signaling in B cell regulation.
Abstract:
In vitro, B cells undergo long term proliferation when triggered through their CD40 surface molecule and in the presence of IL-4. Here, we show that cells that proliferate in this culture system lose their germinal center (GC) features and acquire or maintain non-GC markers. When separated by the magnetic cell separation system, both sIgD+ and sIgD- B cells can proliferate in this culture system, sIgD+ B cells exhibiting a higher rate of growth than sIgD- cells. Simultaneous flow cytometric measurement of sIgD and DNA content revealed that B lymphocytes can keep their sIgD after entry into cell cycle. Experiments using G8 Id-positive B lymphocytes allowed us to follow the evolution of sIgD+ and sIgD- cells in a reconstituted B cell population. Long term proliferating cells are sIgD+/sIgM(+)-derived B lymphocytes whereas the initial sIgD-/sIgM- cells are lost. Taken together, these data show that anti-CD40 + IL-4 activated sIgD+ B blasts express non-GC characteristics and that sIgD+ B cells preferentially proliferate in the CD40 system. The possible in vivo role of IL-4 + CD40 signaling is discussed.