Bystander B cells rapidly acquire antigen receptors from activated B cells by membrane transfer

doi:10.1073/pnas.0800259105

Bystander B cells rapidly acquire antigen receptors from activated B cells by membrane transfer

Divisions of *Immunology and Genetics and
^†Molecular Bioscience, The John Curtin School of Medical Research, Australian National University, Canberra ACT 2601, Australia

Communicated by Gustav J. Nossal, University of Melbourne, Parkville, Victoria, Australia, January 14, 2008 (received for review August 6, 2007)

Abstract

The B cell antigen receptor (BCR) efficiently facilitates the capture and processing of a specific antigen for presentation on MHC class II molecules to antigen-specific CD4⁺ T cells (1). Despite this, the majority of B cells are thought to play only a limited role in CD4⁺ T cell activation because BCRs are clonotypically expressed. Here, we show, however, that activated B cells can, both in vitro and in vivo, rapidly donate their BCR to bystander B cells, a process that is mediated by direct membrane transfer between adjacent B cells and is amplified by the interaction of the BCR with a specific antigen. This results in a dramatic expansion in the number of antigen-binding B cells in vivo, with the transferred BCR endowing recipient B cells with the ability to present a specific antigen to antigen-specific CD4⁺ T cells.

Footnotes

^‡To whom correspondence should be addressed. E-mail: christopher.parish{at}anu.edu.au
Author contributions: B.J.C.Q., V.P.B., V.M., M.D.H., and C.R.P. designed research; B.J.C.Q., V.P.B., and V.M. performed research; K.I.M. contributed new reagents/analytic tools; B.J.C.Q., V.P.B., and V.M. analyzed data; and B.J.C.Q. and C.R.P. wrote the paper.
The authors declare no conflict of interest.
This article contains supporting information online at www.pnas.org/cgi/content/full/0800259105/DC1.