Objective. The premature atherosclerosis seen in patients with systemic lupus erythematosus (SLE) is not explained by traditional risk factors. SLE disease activity, such as renal involvement and presence of autoantibodies, is associated with elevated serum levels of type I interferon (IFN-I), a family of cytokines with potent antiviral and antiproliferative effects. This study was undertaken to test the hypothesis that elevated IFN-I levels could lead to endothelial dysfunction, a surrogate for cardiovascular disease, by causing a reduction in the number of endothelial progenitor cells (EPCs), bone marrow-derived cells that participate in endothelial repair.Methods. EPCs were enumerated in the peripheral blood of SLE patients (n ‫؍‬ 70) and healthy controls (n ‫؍‬ 31), using a colony-forming assay. Serum IFN-I levels were quantified by real-time polymerase chain reaction measurement of the expression of the IFN-I-inducible gene MX1. Endothelial function was determined by peripheral arterial plethysmography.Results. SLE patients had markedly reduced levels of EPC colony-forming units compared with controls (median 5.7/ml peripheral blood [interquartile range 1.9-12.8] versus 28.5/ml peripheral blood [14.7-47.3]; P < 0.0001), and the depletion of EPCs was more dramatic in patients with elevated levels of IFN-I.Stepwise multiple regression analysis showed that MX1 expression and serum levels of C-reactive protein were independently associated with the reduction of EPCs. Importantly, high IFN-I levels were associated with impaired endothelial function in patients with SLE. Conclusion. These data support the novel hypothesis that depletion of EPCs caused by excessive IFN-I may be linked to endothelial dysfunction and increased cardiovascular risk in SLE.It has been firmly established that patients with systemic lupus erythematosus (SLE) are at increased risk of cardiovascular mortality and morbidity (1,2). However, the premature atherosclerosis and endothelial dysfunction in SLE are not solely attributable to traditional cardiovascular risk factors (3,4). Indeed, the risk of developing coronary heart disease remains increased 8-10-fold even after adjustment for risk factors identified in the Framingham Heart Study (3). SLE itself has been determined to be an independent risk factor for endothelial dysfunction, and as many as 40% of patients with lupus exhibit subclinical atherosclerosis (5,6). The cause of the additional risk remains unclear, and factors related to the disease process itself have been implicated.A number of recent studies indicate that type I interferons (IFN-I) are integral to the pathogenesis of SLE (7). Originally characterized with regard to their antiviral properties, the type I IFNs IFN␣ and IFN␤ play important roles in a multitude of immune functions. They exert potent antiproliferative and antiangiogenic effects and are commonly used in cancer treatment (8,9). Antinuclear antibodies, anti-double-stranded

Lymphoid neogenesis is associated with antibody-mediated autoimmune diseases such as Sjogren's syndrome and rheumatoid arthritis. Although systemic lupus erythematosus is the prototypical B-cell-mediated autoimmune disease, the role of lymphoid neogenesis in its pathogenesis is unknown. Intraperitoneal injection of 2,6,10,14-tetramethyl-pentadecane (TMPD, pristane) or mineral oil causes lipogranuloma formation in mice, but only TMPD-treated mice develop lupus. We report that lipogranulomas are a form of lymphoid neogenesis. Immunoperoxidase staining of lipogranulomas revealed B cells, CD4(+) T cells, and dendritic cells and in some cases organization into T- and B-cell zones. Lipogranulomas also expressed the lymphoid chemokines CCL21, CCL19, CXCL13, CXCL12, and CCL22. Expression of the type I interferon (IFN-I)-inducible genes Mx1, IRF7, IP-10, and ISG-15 was greatly increased in TMPD- versus mineral oil-induced lipogranulomas. Dendritic cells from TMPD lipogranulomas underwent activation/maturation with high CD86 and interleukin-12 expression. Magnetic bead depletion of dendritic cells markedly diminished IFN-inducible gene (Mx1) expression. We conclude that TMPD-induced lupus is associated with the formation of ectopic lymphoid tissue containing activated dendritic cells producing IFN-I and interleukin-12. In view of the increased IFN-I production in systemic lupus erythematosus, these studies suggest that IFN-I from ectopic lymphoid tissue could play a role in the pathogenesis of experimental lupus in mice.

Objective Diffuse alveolar hemorrhage (DAH) in lupus patients is >50% fatal. The cause is unknown. The pathogenesis of DAH in C57BL/6 mice with pristane-induced lupus, a model of human lupus-associated DAH, was examined. Methods Clinical/pathological and immunological manifestations DAH in pristane-lupus were compared with human DAH. Tissue distribution of pristane was examined by mass spectrometry. Cell types responsible for disease were determined by in vivo depletion using clodronate liposomes (CloLip) and anti-neutrophil monoclonal antibodies (GR1). The effect of complement depletion with cobra venom factor (CVF) was examined. Results After i.p. injection, pristane migrated to the lung, causing cell death, small vessel vasculitis, and alveolar hemorrhage similar to human DAH. B-cell-deficient mice were resistant to induction of DAH, but susceptibility was restored by infusing IgM. C3-deficient and CD18-deficient mice also were resistant and DAH was prevented in wild-type mice by CVF. Induction of DAH was independent of TLRs, inflammasomes, and inducible nitric oxide (iNOS). Mortality was increased in IL-10-deficient mice and pristane treatment decreased IL-10 receptor expression in monocytes and Stat3 phosphorylation in lung macrophages. In vivo neutrophil depletion was not protective, whereas treatment with CloLip prevented DAH, suggesting that macrophage activation is central to DAH pathogenesis. Conclusion The pathogenesis of DAH involves opsonization of dead cells by natural IgM and complement followed by complement receptor-mediated lung inflammation. The disease is macrophage-dependent and IL-10 is protective. Complement inhibition and/or macrophage-targeted therapies may reduce mortality in lupus-associated DAH.

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IntroductionMore than half of systemic lupus erythematosus (SLE) patients show evidence of excess type I interferon (IFN-I) production, a phenotype associated with renal disease and certain autoantibodies. However, detection of IFN-I proteins in serum is unreliable, and the measurement of interferon-stimulated gene (ISG) expression is expensive and time consuming. The aim of this study was to identify a surrogate marker for IFN-I activity in clinical samples for monitoring disease activity and response to therapy.MethodsMonocyte surface expression of Fcγ receptors (FcγRs), chemokine receptors, and activation markers were analyzed with flow cytometry in whole blood from patients with SLE and healthy controls. FcγR expression also was measured in peripheral blood mononuclear cells (PBMCs) from healthy controls cultured with Toll-like receptor (TLR) agonists, cytokines, or serum from SLE patients. Expression of ISGs was analyzed with real-time PCR.ResultsCirculating CD14+ monocytes from SLE patients showed increased surface expression of FcγRI (CD64). The mean fluorescent intensity of CD64 staining correlated highly with the ISG expression (MX1, IFI44, and Ly6E). In vitro, IFN-I as well as TLR7 and TLR9 agonists, induced CD64 expression on monocytes from healthy controls. Exposure of monocytes from healthy controls to SLE sera also upregulated the expression of CD64 in an IFN-I-dependent manner. Decreased CD64 expression was observed concomitant with the reduction of ISG expression after high-dose corticosteroid therapy.ConclusionsExpression of CD64 on circulating monocytes is IFN-I inducible and highly correlated with ISG expression. Flow-cytometry analysis of CD64 expression on circulating monocytes is a convenient and rapid approach for estimating IFN-I levels in SLE patients.