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Updated: Aug 10, 2026
Generation of Human CD40-activated B cells
Published on: October 17, 2009
The CD40 ligand expressed by human B cells costimulates B cell responses
A C Grammer1, M C Bergman, Y Miura
1Immunology Graduate Program, University of Texas Southwestern Medical Center, Dallas 75235, USA.
Insights
Human B cells express a CD40 ligand identical to that on T cells, crucial for B cell responses. This finding highlights the B cell CD40 ligand
Area of Science:
- Immunology
- Cell Biology
Background:
- Activated B cells play a role in immune responses.
- CD40 is a key receptor in B cell activation.
Purpose of the Study:
- To investigate if activated B cells express a functional CD40 ligand.
- To determine the role of B cell-expressed CD40 ligand in B cell responses.
Main Methods:
- Using purified human peripheral blood B cells, B lymphoblastoid cell lines, and hybridomas.
- Employing a soluble CD40.Ig fusion protein to detect CD40 ligand binding and immunoprecipitation.
- Utilizing RT-PCR to analyze CD40 ligand mRNA sequences.
Main Results:
- Activated B cells and B cell lines bound CD40.Ig, indicating CD40 ligand expression.
- CD40.Ig immunoprecipitated a 33-kDa glycoprotein from activated B cells.
- CD40 ligand mRNA sequences from T cells and B cells were identical.
- CD40.Ig inhibited B cell aggregation and proliferation, while B cell lines expressing CD40 ligand induced Ig production in a CD40-dependent manner.
Conclusions:
- Human B cells express a CD40 ligand identical to that on activated T cells.
- The B cell-expressed CD40 ligand is functionally important for facilitating B cell responses, including Ig production.
Abstract:
The possibility that activated B cells might express a ligand for CD40 that was of functional importance for B cell responses was examined by using highly purified human peripheral blood B cells, as well as a variety of B lymphoblastoid cell lines and hybridomas. Following stimulation with the combination of a calcium ionophore and a phorbol ester, human B cells bound a soluble fusion protein containing the extracellular portion of CD40 and the Fc region of IgG1 (CD40.Ig). A variety of B cell lines and hybridomas also bound CD40.Ig, either constitutively or after activation. In addition, CD40.Ig specifically immunoprecipitated a 33-kDa glycoprotein from surface 125I-labeled activated B cells. The nucleotide sequence of the coding region of the CD40 ligand mRNA amplified by RT-PCR from activated T cells and B cell lines was identical. The CD40 ligand expressed on human B cells was important functionally because homotypic aggregation of CD40 ligand-expressing B cells was inhibited by the CD40.Ig construct. Additionally, RNA and DNA synthesis as well as Ig production by polyclonally activated, highly purified peripheral B cells and a variety of B cell lines were inhibited significantly by the CD40.Ig construct. Finally, B cell lines expressing the CD40 ligand induced Ig production from resting normal B cells in a CD40-dependent manner. These results indicate that human B cells express a ligand for CD40 that is identical with that expressed by activated T cells and that the B cell-expressed CD40 ligand plays an important role in facilitating responses of activated B cells.
