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To investigate the role of interferon regulatory factor-1 (IRF-1) in the development of lupus nephritis, IRF-1(-/-) genotype mice were bred onto the MRL/lpJfas(lpr) (MRL/lpr) background. We examined kidney mesangial cell function and disease progression. Endpoints evaluated included inflammatory mediators, autoantibody production, immune complex deposition, renal pathology, T cell subset analysis, and duration of survival. Mesangial cells cultured from IRF-1(-/-) mice produced significantly lower levels of nitric oxide and IL-12 but not TNF-alpha when stimulated with LPS + IFN-gamma. IRF-1(-/-) mice showed less aggravated dermatitis compared to the wild-type mice. Anti-double-stranded DNA production and proteinuria were significantly decreased in IRF-1(-/-) mice compared to IRF-1(+/+) mice. IgG and C3 deposition as well as glomerulonephritis were decreased in IRF-1(-/-) mice at 26 wk of age compared to the IRF-1(+/+) mice. Splenic CD4- CD8- CD44+ T cells were decreased while CD4+ CD25+ T cells were increased in the IRF-1(-/-) mice when compared to IRF-1(+/+) mice. Survival rates (ED50) were 22 wk for IRF-1(+/+) mice and 45 wk for IRF-1(-/-) mice. These findings suggest an important role of IRF-1 in mediating renal disease in MRL/lpr mice.

Metallosis and metal-induced synovitis are well-recognized complications of metal-backed polyethylene joint prostheses and have been frequently described in the orthopedic surgery literature; however, relatively fewer articles discussing the radiologic aspects of this complication have been published. To illustrate the importance of radiologic findings in the diagnosis and management of these patients, we present a case of metallosis and metal-induced synovitis complicating two revisions of a total knee arthroplasty, caused by polyethylene liner wear and dissociation of the polyethylene liner from the metal-backed patellar prosthesis. Specific attention is given to reviewing signs that aid in diagnosis, such as the "bubble sign," "cloud sign," and "metal-line signs."

Fibroepithelial polyps represent the most common benign ureteral neoplasms. They are an infrequent cause of urinary tract obstruction and patients can present with ipsilateral flank pain with or without hematuria. We report a case of bilateral fibroepithelial polyps causing ureteropelvic junction obstruction in a child.