Loss of IRF-4–binding protein leads to the spontaneous development of systemic autoimmunity
Jessica C. Fanzo, … , Steven Greenberg, Alessandra B. Pernis
Jessica C. Fanzo, … , Steven Greenberg, Alessandra B. Pernis
Published March 1, 2006
Citation Information: J Clin Invest. 2006;116(3):703-714. https://doi.org/10.1172/JCI24096.
View: Text | PDF
Research Article Immunology

Loss of IRF-4–binding protein leads to the spontaneous development of systemic autoimmunity

Abstract

IFN regulatory factor 4–binding (IRF-4–binding) protein (IBP) is a novel type of activator of Rho GTPases that is recruited to the immunological synapse upon TCR stimulation. Here we demonstrate that loss of IBP leads to the spontaneous development of a systemic autoimmune disorder characterized by the accumulation of effector/memory T cells and IgG+ B cells, profound hypergammaglobulinemia, and autoantibody production. Similar to human SLE, this syndrome primarily affects females. T cells from IBP-deficient mice are resistant to death in vitro as well as in vivo and exhibit selective defects in effector function. In the absence of IBP, T cells respond suboptimally to TCR engagement, as demonstrated by diminished ERK1/2 activation, decreased c-Fos induction, impaired immunological synapse formation, and defective actin polymerization. Transduction of IBP-deficient T cells with a WT IBP protein, but not with an IBP mutant lacking the Dbl-like domain required for Rho GTPase activation, rescues the cytoskeletal defects exhibited by these cells. Collectively, these findings indicate that IBP, a novel regulator of Rho GTPases, is required for optimal T cell effector function, lymphocyte homeostasis, and the prevention of systemic autoimmunity.

Authors

Jessica C. Fanzo, Wen Yang, So Young Jang, Sanjay Gupta, Qinzhong Chen, Ayesha Siddiq, Steven Greenberg, Alessandra B. Pernis

×

Figure 4

T cells are resistant to apoptosis.

Options: View larger image (or click on image) Download as PowerPoint
IBPtrap/trap T cells are resistant to apoptosis. (A) Proliferation of T ...
(A) Proliferation of T cells from WT and IBP mutant mice. Cells were stimulated with plate-bound anti-CD3ε (2C11) (1 μg/ml) and soluble anti-CD28 (1 μg/ml) antibodies or with PMA (50 ng/ml) plus ionomycin (1 μM) for 48 hours. The culture was then pulsed with [3H]thymidine for 18 hours. This experiment is representative of 5 independent experiments. The data were analyzed using 2-tailed Student’s t test. A statistical probability of P < 0.05 was considered significant. *P < 0.05; **P < 0.005 (IBPtrap/trap versus WT). (B) Apoptosis of IBP+/+ and IBPtrap/trap T cells upon CD3 restimulation. Purified naive CD4+ T cells from IBP+/+ (black bars) or IBPtrap/trap (white bars) mice were stimulated for 3 days and then harvested. The cells were then restimulated with either IL-2 alone or IL-2 with anti-CD3 mAbs at the indicated doses for 24 hours. Cells were then stained with propidium iodide, and the percentage of apoptotic cells was determined by quantification of the sub-G0 population by FACS. Each assay was conducted in duplicate. The experiment is representative of 3 separate experiments. (C) SEB-specific deletion of T cells in IBPtrap/trap mice. IBP+/+ (n = 4) (filled circles) and IBPtrap/trap (n = 4) (open circles) mice were injected i.p. with SEB on day 0. Peripheral blood cells were stained with antibodies against Vβ8 and CD4 (left panel) or Vβ6 and CD4 (right panel) and analyzed by FACS at the indicated time points. Results are expressed as a mean ± SD. Statistical differences were determined using 2-tailed Student’s t test. (D) Loss of mitochondrial potential. Purified naive CD4+ T cells from IBP+/+ (black bars) or IBPtrap/trap (white bars) mice were stimulated for 3 days and then harvested. The cells were then restimulated with either IL-2 alone or IL-2 with anti-CD3 mAbs at 10 μg/ml for 24 hours. Cells were then stained with Mitotracker Deep Red 633 to assess loss of mitochondrial potential. The percentage of cells that displayed a decrease in intensity of staining (Mitotracker lo T cells) is indicated. The experiment is representative of 3 separate experiments. Results are expressed as mean ± SD. Statistical differences were determined using 2-tailed Student’s t test.