| The conventional view of B cells in systemic autoimmunity is that they promote lupus by producing autoantibodies (autoAb). However, this view is incomplete because recent studies have revealed that autoimmune disease can be dissociated from autoAb-deposition (1--3). Furthermore, the spontaneous T cell activation and organ infiltration in systemic lupus erythematosus (SLE) patients and animal models are difficult to explain entirely via a direct autoAb-mediated mechanism. In this dissertation, we describe work addressing the B cell functions of autoantigen-presentation and autoAb production in lupus pathogenesis. In the JHD-MRL-Fas lpr strain (JHD/lpr), a B cell-deficient version of the lupus-prone MRL-Faslpr (MRL/ lpr) mouse, spontaneous nephritis and dermatitis is abrogated, demonstrating that B cells have a primary role in disease. B cells play a similar role in Fas-intact, lupus-prone MRL mice (MRL/+). To address the role of autoantigen- presentation, we analyzed transgenic mice which have B cells that cannot secrete immunoglobulin (mIgM transgenic mice). The restoration of B cells without antibody caused substantial interstitial nephritis and vasculitis although less marked than the intact MRL/lpr controls. To address the role of autoAb, we infused serum from aged MRL/lpr mice into JHD/lpr mice. At most, mild to no nephritis was observed in the infused mice. Finally, we analyzed the role of B cells in promoting lupus dermatitis. Our findings indicated that skin lesions are absent in B cell-deficient MRL/lpr and MRL/+ mice, indicating that B cells are required for lupus dermatitis, independent of Fas. These results support that B cells are promoting autoimmunity in mechanisms other than autoAb secretion, and we describe a model depicting these B cell roles in the context of other inflammatory events in lupus. |
