International Immunology Advance Access originally published online on November 15, 2005
International Immunology 2006 18(1):69-78; doi:10.1093/intimm/dxh350
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Lack of induced co-stimulation as a result of complement receptor 2 (CR2) ligation on mouse splenic B cells
Institute for Immunology and Infection Research, School of Biological Sciences, University of Edinburgh, Ashworth Laboratories, West Mains Road, Edinburgh EH9 3JT, UK
1 Present address: Lab901 Ltd, Unit 53, IMEX Business Centre, Bilston Glen Industrial Estate, Loanhead, Midlothian EH20 9LZ, UK
2 Present address: School of Surgical and Reproductive Sciences, Faculty of Medical Sciences, University of Newcastle upon Tyne, 3rd Floor, William Leech Building, Framlington Place, Newcastle upon Tyne NE2 4HH, UK
Correspondence to: A. M. Knight; E-mail: andrew.knight{at}ncl.ac.uk
B cells act as efficient antigen-presenting cells if they acquire antigen via membrane-bound Ig [termed the B cell receptor (BCR)]. Ligation of the BCR leads to antigen internalization, processing and presentation to CD4+ T cells in association with MHC class II molecules. Ligation of the BCR also leads to the generation of activation signals. One short-term consequence of this is the up-regulation of co-stimulatory molecule expression by the B cell, allowing full T cell activation. Other antigen receptors expressed by B cells can also mediate efficient antigen presentation to CD4+ T cells. Ligating one such receptor, complement receptor 2 (CR2), has also been described to induce co-stimulatory molecule expression. If correct, this may have serious consequences for ensuring the specificity of the resultant B cell response. We have therefore investigated the effects of ligating both the BCR and CR2 independently of each other, as well as with reagents to cross-link the two receptors, in order to clarify these findings. In contrast to the effects seen upon BCR ligation, we find no evidence for co-stimulatory molecule up-regulation following CR2 ligation. As antigen presentation in the absence of co-stimulation may lead to the induction of tolerogenic or regulatory signals being delivered to T cell populations, these findings imply that the role of CR2 in B cell-mediated antigen presentation is different from that of the BCR.
Keywords: activation, antigen processing/presentation, BCR