Mechanisms of B cell autoimmunity in SLE
1 Charite Center 12, Department of Medicine/Rheumatology and Clinical Immunology, Charite Universitätsmedizin Berlin and Deutsches Rheumaforschungszentrum, Chariteplatz 01, 10117 Berlin, Germany
2 Formerly National Institute of Arthritis and Musculoskeletal and Skin Diseases, National Institutes of Health, 9000 Rockville Pike, Bethesda, MD 20892, USA
Arthritis Research & Therapy 2011, 13:243 doi:10.1186/ar3433Published: 27 October 2011
Systemic lupus erythematosus (SLE) is a systemic autoimmune disease that is known to be associated with polyclonal B-cell hyperreactivity. The underlying causes of the diffuse B-cell over-reactivity are unclear, but potential candidates include (a) intrinsic hyper-reactivity leading to polyclonal B-cell activation with disturbed activation thresholds and ineffective negative selection; (b) lack of immunoregulatory functions; (c) secondary effects of an overactive inflammatory environment, such as overactive germinal center and ectopic follicular activity; and/or (d) disturbed cytokine production by non-B immune cells. These mechanisms are not mutually exclusive and may operate to varying extents and at varying times in SLE. Phenotypic and molecular studies as well as the results of recent clinical trials have begun to provide new insights to address these possibilities. Of importance, new information has made it possible to distinguish between the contribution played by abnormalities in central checkpoints that could lead to a pre-immune repertoire enriched in autoreactive B cells, on the one hand, and the possibility that autoimmunity arises in the periphery from somatic hypermutation and abnormal selection during T cell-dependent B-cell responses on the other. There is an intriguing possibility that apoptotic material bound to the surface of follicular dendritic cells positively selects autoreactive B cells that arise from non-autoreactive B-cell precursors as a result of somatic hypermutation and thereby promotes the peripheral emergence of autoimmunity.