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Int Immunol. 2009 Nov;21(11):1225-37. doi: 10.1093/intimm/dxp090. Epub 2009 Sep 7.

Enhanced B cell activation in the absence of CD81.

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Division of Oncology, Department of Medicine, Stanford University School of Medicine, Stanford, CA 94305, USA.


CD81 is a component of the CD19/CD21 co-receptor complex in B cells. However, the role of CD81 in B cell activation has not been clearly elucidated. Here, we demonstrate that Cd81(-/-) B cells stimulated via their B cell receptor fluxed higher intracellular-free calcium ion along with increased phosphorylation of spleen tyrosine kinase and phospholipase gamma 2. Additionally, Cd81(-/-) B cells responded to toll like receptor 4 stimulation with increased nuclear factor-kappa B activation, cell proliferation and antibody secretion compared with wild-type B cells. Cd81(-/-) mice also mounted a significantly higher immune response to T-independent antigens than their wild-type counterparts. Finally, analysis of Cd81(-/-) B cells that were generated by bone marrow transplantation into Rag1(-/-) mice confirmed that the hyperactive phenotype is not dependent on the CD81-deficient environment. Taken together, these results indicate that CD81 plays a negative role in B cell activation in vitro and in vivo.

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