Medical Biology - Research Publications
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ItemNo Preview AvailableAn Slfn2 mutation causes lymphoid and myeloid immunodeficiency due to loss of immune cell quiescence(NATURE PUBLISHING GROUP, 2010-04)Here we describe a previously unknown form of inherited immunodeficiency revealed by an N-ethyl-N-nitrosourea-induced mutation called elektra. Mice homozygous for this mutation showed enhanced susceptibility to bacterial and viral infection and diminished numbers of T cells and inflammatory monocytes that failed to proliferate after infection and died via the intrinsic apoptotic pathway in response to diverse proliferative stimuli. They also had a greater proportion of T cells poised to replicate DNA, and their T cells expressed a subset of activation markers, suggestive of a semi-activated state. We positionally ascribe the elektra phenotype to a mutation in the gene encoding Schlafen-2 (Slfn2). Our findings identify a physiological role for Slfn2 in the defense against pathogens through the regulation of quiescence in T cells and monocytes.
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ItemNo Preview AvailableIL-6 promotes acute and chronic inflammatory disease in the absence of SOCS3(NATURE PUBLISHING GROUP, 2012-01)The lack of expression of the suppressor of cytokine signalling-3 (SOCS3) or inactivation of the negative regulatory capacity of SOCS3 has been well documented in rheumatoid arthritis, viral hepatitis and cancer. The specific qualitative and quantitative consequences of SOCS3 deficiency on interleukin-6 (IL-6)-mediated pro- and anti-inflammatory responses remain controversial in vitro and unknown in vivo. Mice with a conditional deletion of SOCS3 in hematopoietic cells develop lethal inflammatory disease during adult life and develop gross histopathological changes during experimental arthritis, typified by elevated IL-6 levels. To clarify the nature of the IL-6 responses in vivo, we generated mice deficient in SOCS3 (SOCS3(-/Δvav)) or both SOCS3 and IL-6 (IL-6(-/-)/SOCS3(-/Δvav)), and examined responses in models of acute and chronic inflammation. Acute responses to IL-1β were lethal to SOCS3(-/Δvav) mice but not IL-6(-/-)/SOCS3(-/Δvav) mice, indicating that IL-6 was required for the lethal inflammation induced by IL-1β. Administration of IL-1β to SOCS3(-/Δvav) mice induced systemic apoptosis of lymphocytes in the thymus, spleen and lymph nodes that was dependent on the presence of IL-6. IL-6 deficiency prolonged survival of SOCS3(-/Δvav) mice and ameliorated spontaneous inflammatory disease developing during adult life. Infection of SOCS3(-/Δvav) mice with LCMV induced a lethal inflammatory response that was dependent on IL-6, despite SOCS3(-/Δvav) mice controlling viral replication. We conclude that SOCS3 is required for survival during inflammatory responses and is a critical regulator of IL-6 in vivo.
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ItemTranslation inhibitors induce cell death by multiple mechanisms and Mcl-1 reduction is only a minor contributor(NATURE PUBLISHING GROUP, 2012-10)There is significant interest in treating cancers by blocking protein synthesis, to which hematological malignancies seem particularly sensitive. The translation elongation inhibitor homoharringtonine (Omacetaxine mepesuccinate) is undergoing clinical trials for chronic myeloid leukemia, whereas the translation initiation inhibitor silvestrol has shown promise in mouse models of cancer. Precisely how these compounds induce cell death is unclear, but reduction in Mcl-1, a labile pro-survival Bcl-2 family member, has been proposed to constitute the critical event. Moreover, the contribution of translation inhibitors to neutropenia and lymphopenia has not been precisely defined. Herein, we demonstrate that primary B cells and neutrophils are highly sensitive to translation inhibitors, which trigger the Bax/Bak-mediated apoptotic pathway. However, contrary to expectations, reduction of Mcl-1 did not significantly enhance cytotoxicity of these compounds, suggesting that it does not have a principal role and cautions that strong correlations do not always signify causality. On the other hand, the killing of T lymphocytes was less dependent on Bax and Bak, indicating that translation inhibitors can also induce cell death via alternative mechanisms. Indeed, loss of clonogenic survival proved to be independent of the Bax/Bak-mediated apoptosis altogether. Our findings warn of potential toxicity as these translation inhibitors are cytotoxic to many differentiated non-cycling cells.
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ItemThe Role of Neutrophils during Mild and Severe Influenza Virus Infections of Mice(PUBLIC LIBRARY SCIENCE, 2011-03-14)Neutrophils have been implicated in both protective and pathological responses following influenza virus infections. We have used mAb 1A8 (anti-Ly6G) to specifically deplete LyG6(high) neutrophils and induce neutropenia in mice infected with virus strains known to differ in virulence. Mice were also treated with mAb RB6-8C5 (anti-Ly6C/G or anti-Gr-1), a mAb widely used to investigate the role of neutrophils in mice that has been shown to bind and deplete additional leukocyte subsets. Using mAb 1A8, we confirm the beneficial role of neutrophils in mice infected with virus strains of intermediate (HKx31; H3N2) or high (PR8; H1N1) virulence whereas treatment of mice infected with an avirulent strain (BJx109; H3N2) did not affect disease or virus replication. Treatment of BJx109-infected mice with mAb RB6-8C5 was, however, associated with significant weight loss and enhanced virus replication indicating that other Gr-1(+) cells, not neutrophils, limit disease severity during mild influenza infections.
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ItemNeutrophils Require SHP1 To Regulate IL-1β Production and Prevent Inflammatory Skin Disease(AMER ASSOC IMMUNOLOGISTS, 2011-01-15)The regulation of neutrophil recruitment, activation, and disposal is pivotal for circumscribed inflammation. SHP1(Y208N/Y208N) mutant mice develop severe cutaneous inflammatory disease that is IL-1R dependent. Genetic reduction in neutrophil numbers and neutrophilic responses to infection is sufficient to prevent the spontaneous initiation of this disease. Neutrophils from SHP1(Y208N/Y208N) mice display increased pro-IL-1β production due to altered responses to MyD88-dependent and MyD88-independent signals. The IL-1R-dependent inflammatory disease in SHP1(Y208N/Y208N) mice develops independently of caspase 1 and proteinase 3 and neutrophil elastase. In response to Fas ligand, a caspase 1-independent inducer of IL-1β production, neutrophils from SHP1(Y208N/Y208N) mice produce elevated levels of IL-1β but display reduced caspase 3 and caspase 7 activation. In neutrophils deficient in SHP1, IL-1β induces high levels of pro-IL-1β suggesting the presence of a paracrine IL-1β loop. These data indicate that the neutrophil- and IL-1-dependent disease in SHP1(Y208N/Y208N) mice is a consequence of loss of negative regulation of TLR and IL-1R signaling.
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