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Updated: Aug 8, 2026
Murine Model of CD40-activation of B cells
Published on: March 6, 2010
Tumor necrosis factor-alpha and CD40L modulate cell surface morphology and induce aggregation in Ramos Burkitt's
Reuven Laskov1, Nir Berger, Matthew D Scharff
1Department of Experimental Medicine and Cancer Research, Hebrew University-Hadassah Medical School, Jerusalem, Israel. laskov@md.huji.ac.il
Insights
Tumor necrosis factor-alpha (TNF-alpha) and CD40 ligand (CD40L) enhance B-cell aggregation and adhesion by increasing cell surface projections. These cytokines upregulate intercellular adhesion molecule-1 and Fas receptor expression on B cells via TNF-R1.
Area of Science:
- Immunology
- Cell Biology
- Molecular Biology
Background:
- CD40L-CD40 interaction is crucial for B-cell signaling, differentiation, and immunoglobulin gene expression.
- The effects of tumor necrosis factor-alpha (TNF-alpha) on B-cell signaling through TNF-R1 and TNF-R2 are less understood.
Purpose of the Study:
- To investigate the direct effects of TNF-alpha and CD40L on B-cell signaling and morphology.
- To elucidate the role of TNF-R1 and TNF-R2 in mediating TNF-alpha's effects on B cells.
Main Methods:
- Utilized Ramos Burkitt's lymphoma cell line as a model system.
- Treated cells with TNF-alpha, CD40L, IL-4, IFN-gamma, and TGF-beta.
- Employed scanning electron microscopy, reverse transcriptase-polymerase chain reaction, and flow cytometry.
Main Results:
- TNF-alpha and CD40L, but not other tested cytokines, enhanced B-cell aggregation and adherence.
- These cytokines increased the number and complexity of cell surface membrane projections (microvilli, filopodia, ruffled membranes).
- TNF-alpha and CD40L upregulated intercellular adhesion molecule-1 and Fas receptor expression, with TNF-alpha acting primarily through TNF-R1.
Conclusions:
- TNF-alpha and CD40L significantly modulate B-cell surface morphology and adhesion properties.
- The findings highlight the distinct roles of TNF-alpha and CD40L in B-cell activation and interaction.
- Ramos cells express TNF-R1, mediating TNF-alpha's effects on cell adhesion and surface morphology.
Abstract:
Interaction of CD40L and its cognate receptor is an essential component of B-lymphocyte signaling, affecting various aspects of B-cell differentiation pathways and immunoglobulin gene expression. However, much less is known about the biological consequences of B-cell signaling through tumor necrosis factor (TNF)-alpha and its cognate receptors TNF-R1 and 2. We used Ramos Burkitt's lymphoma cell line as a model system to study the direct effects of these cytokines on B cells. Treatment of Ramos cells with either TNF-alpha or CD40L, but not with interleukin (IL)- 4, interferon (IFN)-gamma and transforming growth factor (TGF)-beta, resulted in enhanced cell aggregation and enhancement of adherence to glass cover-slips. Scanning electron microscopy showed that Ramos cells have a polarized cell surface morphology and exhibit at least 3 cell surface morphological domains: microvilli, filopodia and ruffled membranes. The cells adhered to the glass matrix through multiple filopodia/podopodia-like cell processes and demonstrated distinct ruffled-like membrane projections on their opposite pole. Induction by TNF-alpha or CD40L, but not with IL-4, IFN-gamma and TGF-beta, resulted in increased number and complexity of both types of membrane projections. TNF-alpha and CD40L upregulated the expression of the adhesion molecule intercellular adhesion molecule-1 and the Fas receptor on Ramos cells, without affecting the expression levels of membrane immunoglobulin M or its secretion rate. Reverse transcriptase-polymerase chain reaction, and flow cytometry demonstrated that Ramos cells expressed TNF-R1 but very little if any TNF-R2, indicating that TNF-alpha exerted its effects on Ramos cells through the former receptor.
