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Updated: Aug 9, 2026
Generation of Human CD40-activated B cells
Published on: October 17, 2009
CD48 delivers an accessory signal for CD40-mediated activation of human B cells
E N Klyushnenkova1, L Li, R J Armitage
1Laboratory of Cellular Immunology, Alton Ochsner Medical Foundation, New Orleans, Louisiana 70121, USA.
Insights
CD48 enhances T cell activation signals in human B cells, boosting responses to IL-4 and IL-10. This molecule, CD48, works with CD40 to improve B cell aggregation, proliferation, and antibody secretion.
Area of Science:
- Immunology
- Cell Biology
Background:
- CD48 is a T cell surface protein ligand expressed on human T and B cells.
- The precise function of CD48 in B cell activation remains largely unknown.
Purpose of the Study:
- To investigate the role of CD48 in delivering activating signals to human B cells.
- To determine if CD48 costimulation enhances CD40-mediated B cell activation.
Main Methods:
- Utilized anti-CD48 and anti-CD40 antibodies for costimulation assays on human tonsillar B cells.
- Assessed B cell aggregation, proliferation, and IgG secretion.
- Analyzed protein tyrosine phosphorylation and expression of CD23 and CD25.
Main Results:
- Anti-CD48 costimulation significantly enhanced CD40-mediated B cell activation, including aggregation, proliferation, and IgG secretion.
- CD48-mediated costimulation required IL-4 and/or IL-10, but not IL-2.
- Ligation of CD48 induced CD23 expression on IL-4-stimulated B cells and triggered protein tyrosine phosphorylation, albeit later than CD40.
Conclusions:
- CD48 acts as a costimulatory molecule that enhances activating signals initiated by CD40 in human B cells.
- CD48 signaling increases B cell responsiveness to IL-4 and IL-10, contributing to immune responses.
Abstract:
CD48, a glycosyl phosphatidylinositol anchored molecule has recently been shown to be a ligand for the T cell surface protein CD2 in mouse, human, and rat. It is expressed on practically all human T and B cells; however, its function remains unknown. We examined whether CD48 may be involved in the delivery of activating signals to human B cells. Costimulation with anti-CD48 J4-57 significantly increased CD40-mediated activation of tonsillar B cells. Costimulatory effect of anti-CD48 was observed on B cell aggregation, proliferation, and IgG secretion. Anti-CD48 alone did not stimulate resting B cells. Accessory signal provided through CD48 required the presence of IL-4 and/or IL-10, whereas responses of B cells to IL-2 was not affected. Ligation of CD48 by specific antibody induced CD23 expression on IL-4-stimulated Ramos B cell line but did not affect expression of CD25. We also examined the biochemical nature of the costimulatory effect of anti-CD40 and CD48. Ligation of CD40 or CD48 on the B cells induced tyrosine phosphorylation of proteins. CD40 induced earlier changes in the protein phosphorylation than CD48 did. Taken together, our data suggest that the stimulation via CD40 provides initial signals to activate B cells and CD48 may be involved in enhancing the activating signal to B cells, resulting in increased responsiveness of B cells to IL-4 and IL-10.
