Published online October 29, 2007
doi:10.1084/jem.20071268
The Journal of Experimental Medicine, Vol. 204, No. 12, 2853-2864
The Rockefeller University Press, 0022-1007 $30.00
© 2007 Lamoureux et al.
Reduced receptor editing in lupus-prone MRL/lpr mice
Jennifer L. Lamoureux,
Lisa C. Watson,
Marie Cherrier,
Patrick Skog,
David Nemazee, and
Ann J. Feeney
Department of Immunology, The Scripps Research Institute, La Jolla, CA 92037
CORRESPONDENCE Ann J. Feeney: feeney{at}scripps.edu
The initial B cell repertoire contains a considerable proportion of autoreactive specificities. The first major B cell tolerance checkpoint is at the stage of the immature B cell, where receptor editing is the primary mode of eliminating self-reactivity. The cells that emigrate from the bone marrow have a second tolerance checkpoint in the transitional compartment in the spleen. Although it is known that the second checkpoint is defective in lupus, it is not clear whether there is any breakdown in central B cell tolerance in the bone marrow. We demonstrate that receptor editing is less efficient in the lupus-prone strain MRL/lpr. In an in vitro system, when receptor-editing signals are given to bone marrow immature B cells by antiidiotype antibody or after in vivo exposure to membrane-bound self-antigen, MRL/lpr 3-83 transgenic immature B cells undergo less endogenous rearrangement and up-regulate recombination activating gene messenger RNA to a lesser extent than B10 transgenic cells. CD19, along with immunoglobulin M, is down-regulated in the bone marrow upon receptor editing, but the extent of down-regulation is fivefold less in MRL/lpr mice. Less efficient receptor editing could allow some autoreactive cells to escape from the bone marrow in lupus-prone mice, thus predisposing to autoimmunity.
Abbreviations used: APC, allophycocyanin; BCR, B cell receptor; cDNA, complementary DNA; MFI, mean fluorescence intensity; mRNA, messenger RNA; RS, recombining sequence; SLE, systemic lupus erythematosus.

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