Arthritis & Rheumatism, Volume 62,
November 2010 Abstract Supplement

Abstracts of the American College of
Rheumatology/Association of Rheumatology Health Professionals
Annual Scientific Meeting
Atlanta, Georgia November 6-11, 2010.


IRF4-Deficient Lupus-Prone MRL/lpr Mice Lack Serum Ig/Auto-Abs and Th17 Cells but Develop Non-Immune Complex-Mediated Diffuse Proliferative Glomerulonephritis and Dermatitis/Ear Necrosis.

Sekine4,  Hideharu, Machida1,  Takeshi, Suzuki3,  Eiji, Avila3,  Efrain Martinez, Ruiz5,  Phil, Reilly6,  Christopher M., Gilkeson2,  Gary S.

Fukushima Medical University, Fukushima, Japan
Med Univ of South Carolina, Charleston, SC
Medical University of South Carolina, Charleston, SC
Medical University of South Carolina/Fukushima Medical University, Charleston, SC
University of Miami, Miami, FL
Virginia Tech, VA

The transcription factor interferon regulatory factor 4 (IRF4) is a member of the IRF family of transcription regulators and required for Ig-production/maturation of B cells and development of Th17 cells. We found that the Irf4 gene is over-expressed in CD4+ T cells in lupus-prone MRL/lpr mice compared to non-lupus mice. To investigate the role of IRF4 in the development of lupus, we analyzed disease expression in Irf4-/- MRL/lpr mice until time of sacrifice.

Sera and urine were collected biweekly from groups of Irf4-/- and wild-type MRL/lpr mice starting at 12 weeks. Serum Ig/anti-dsDNA Ab levels and urinary albumin excretion levels were measured by ELISA. Mice were sacrificed at 24 weeks of age and ear, back skin and kidneys were removed for pathological analysis. Splenic immune cell populations were analyzed by flow. To determine Th1/Th2/Th17 cell numbers, splenic CD4+ T cells from 12 weeks old MRL/lpr mice were purified by magnetic selection, cultured with PMA/ionomycin, and IFN-g, IL-4 or IL-17 production was detected by flow and ELISPOT assay.

Unlike wild-type MRL/lpr mice, all Irf4-/- MRL/lpr mice had undetectable levels of serum Ig and anti-dsDNA Abs and no albuminuria. Irf4-/- MRL/lpr mice had no glomerular immune complex (IC)/C3 deposits, epithelial cell reaction, crescent formation or renal vasculitis, however, they had significant dermatitis/ear necrosis and pathologic observable nephritis characterized by diffuse glomerular hypercellularity and mesangial matrix expansion consistent with diffuse proliferative glomerulonephritis. Irf4-/- MRL/lpr mice showed significantly increased numbers of splenic CD4+ T cells (66.7±6.6×106 vs 41.4±5.8×106; p= 0.016) while all other splenic immune cells were significantly decreased compared to wild-type controls. Notably, splenic CD19+/IgM+ B cells and CD8+ T cells were significantly decreased/absent in Irf4-/- MRL/lpr mice compared to wild-type MRL/lpr mice. Bone marrow analysis revealed B cell development arrest before the stage of CD19+/B220high/CD43low immature B cells in Irf4-/- MRL/lpr mice. Flow/ELISOPT assay showed absence of IL-17 producing cells in Irf4-/- MRL/lpr mice, however, they had significantly increased numbers of IFN-g producing cells (59.2±20.2×106 vs 6.6±1.5×106; p= 0.027) and IL-4 producing cells (4.30±0.27×106 vs 0.39±0.08×106; p < 0.0001) compared to control MRL/lpr mice.

Our results indicate that IRF4 is required for the full expression of lupus like renal disease in MRL/lpr mice, most likely by maintenance/modulation of autoreactive B cells and specific T cell subsets. Importantly, development of proliferative glomerulonephritis and skin disease were still present in Irf4-/- MRL/lpr mice indicating that their pathogenesis, in these mice, is independent of autoAb/IC-mediated mechanisms or Th17 cells, and is most likely induced by Th1 and/or Th2 cells. Absence of IL-17 producing CD4+ T cells and significantly increased numbers of IFN-g or IL-4 producing CD4+ T cells in the spleens of Irf4-/- MRL/lpr mice suggested a dual role of IRF4 for development of Th17 cells and inhibition of Th1 and Th2 cell development in MRL/lpr mice.

To cite this abstract, please use the following information:
Sekine, Hideharu, Machida, Takeshi, Suzuki, Eiji, Avila, Efrain Martinez, Ruiz, Phil, Reilly, Christopher M., et al; IRF4-Deficient Lupus-Prone MRL/lpr Mice Lack Serum Ig/Auto-Abs and Th17 Cells but Develop Non-Immune Complex-Mediated Diffuse Proliferative Glomerulonephritis and Dermatitis/Ear Necrosis. [abstract]. Arthritis Rheum 2010;62 Suppl 10 :435
DOI: 10.1002/art.28204

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