Intravenous immunoglobulin (IVIg) is an effective treatment against immune thrombocytopenia (ITP). Previous studies suggested that IVIg exerts this ame IntroductionImmune thrombocytopenia (ITP) is a disorder manifested by immune-mediated low platelet (PLT) counts. 1-3 Treatment with high-dose intravenous immunoglobulin (IVIg), a human IgG fraction prepared from pools of plasma of thousands of donors, can rapidly relieve the symptoms of thrombocytopenia. 2,4 The PLT clearance is mainly mediated through IgG Fc receptors (Fc␥R) bearing macrophages in the mononuclear phagocytic system (MPS). 5 In mice, both inhibitory and activating Fc␥Rs, the Fc␥RIIB and Fc␥RIII (encoded by Fcgr2b and Fcgr3, respectively) are important for IVIg-mediated amelioration. [6][7][8] IVIg treatment was shown to induce macrophages expressing Fc␥RIIB, by which it reduced the phagocytic activity of the macrophages. 5,7,8 In addition, Fc␥RIII on CD11c ϩ dendritic cells (DCs) is important for IVIg-mediated amelioration of ITP in a 2-step priming model, in which IVIg could modulate effector leukocytes indirectly through initiator DCs. 5,9 The modulation of PLTs, however, is less characterized. The splenic MPS plays important roles in the phagocytic clearance of PLT during ITP, 1,10,11 suggesting that the severity of ITP is associated with PLT-phagocyte engagements. Thus, we established a flow cytometry-based PLT-splenic CD14 ϩ leukocyte (PLT-CD14 ϩ LC) engagement analysis to investigate the roles of PLTs and phagocytes in IVIg-primed DCs (IVIg-DCs)-mediated modulations. The involvements of P-selectin, Fc␥RIIB, and Fc␥RIII in the amelioration of ITP are discussed. Methods IVIg and miceIVIg was purchased from Bayer (Gamimune N) and CSL Limited Inc. The C57BL/6J mice (males, 7-10 weeks old) were purchased from the National Laboratory Animal Center (NLAC). C57BL/6J mice deficient in Fc␥RIII (B6;129P2-Fcgr3 tm1Sjv /J), Fc␥RIIB (B6;129S4-Fcgr2b tm1Rav /J), and Pselectin (B6;129S2-Selp tm1Hyn /J), were purchased from The Jackson Laboratory. Mice were housed in the Laboratory Animal Center of Tzu Chi University. The research methods were approved by the Animal Care and Use Committee of Tzu-Chi University. Induction and reversal of murine ITPITP was induced and treated as previously described. 7 Mice were intravenously injected with 0.1 mg/kg body weight of anti-PLT monoclonal antibody (mAb, rat anti-mouse integrin ␣ IIb /CD41 Ig, clone MWReg30; BD Biosciences) to induce ITP in all experiments, except for the low-dose treatments of MWReg30 (0.03 mg/kg) described in supplemental Figure 1 (available on the Blood web site; see the Supplemental Materials link at the top of the online article). To analyze PLT counts, whole blood samples (50-100 L) of mice were collected from the retro-orbital venous plexus and mixed with anticoagulant ACD solution (38mM citric acid, 75mM sodium citrate, 100mM dextrose) in Eppendorf tubes. PLT counts were then measured with a hematology analyzer (KX-21N; Sysmex) at various time intervals (0, 2, 4, and 24 hours after anti-CD41...

Psychological stress increases the risk of gastrointestinal (GI) tract diseases, which involve bidirectional communication of the GI and nerves systems. Acute stress leads to GI ulcers; however, the mechanism of the native cellular protection pathway, which safeguards tissue integrality and maintains GI homeostasis, remains to be investigated. In a mouse model of this study, restraint stress induced GI leakage, abnormal tight junction protein expression, and cell death of gut epithelial cells. The expression of activating transcription factor 3 (ATF3), a stress-responsive transcription factor, is upregulated in the GI tissues of stressed animals. ATF3-deficient mice displayed an exacerbated phenotype of GI injuries. These results suggested that, in response to stress, ATF3 is part of the native cellular protective pathway in the GI system, which could be a molecular target for managing psychological stress-induced GI tract diseases.

In tropical and subtropical regions, mosquito-borne dengue virus (DENV) infections can lead to severe dengue, also known as dengue hemorrhage fever, which causes bleeding, thrombocytopenia, and blood plasma leakage and increases mortality. Although DENV-induced platelet cell death was linked to disease severity, the role of responsible viral factors and the elicitation mechanism of abnormal platelet activation and cell death remain unclear. DENV and virion-surface envelope protein domain III (EIII), a cellular binding moiety of the virus particle, highly increase during the viremia stage. Our previous report suggested that exposure to such viremia EIII levels can lead to cell death of endothelial cells, neutrophils, and megakaryocytes. Here we found that both DENV and EIII could induce abnormal platelet activation and predominantly necrotic cell death pyroptosis. Blockages of EIII-induced platelet signaling using the competitive inhibitor chondroitin sulfate B or selective Nlrp3 inflammasome inhibitors OLT1177 and Z-WHED-FMK markedly ameliorated DENV- and EIII-induced thrombocytopenia, platelet activation, and cell death. These results suggest that EIII could be considered as a virulence factor of DENV, and that Nlrp3 inflammasome is a feasible target for developing therapeutic approaches against dengue-induced platelet defects.

Typically occurring during secondary dengue virus (DENV) infections, dengue hemorrhagic fever (DHF) causes abnormal immune responses, as well as endothelial vascular dysfunction, for which the responsible viral factor remains unclear. During peak viremia, the plasma levels of virion-associated envelope protein domain III (EIII) increases to a point at which cell death is sufficiently induced in megakaryocytes in vitro. Thus, EIII may constitute a virulence factor for endothelial damage. In this study, we examined endothelial cell death induced by treatment with DENV and EIII in vitro. Notably, pyroptosis, the major type of endothelial cell death observed, was attenuated through treatment with Nlrp3 inflammasome inhibitors. EIII injection effectively induced endothelial abnormalities, and sequential injection of EIII and DENV-NS1 autoantibodies induced further vascular damage, liver dysfunction, thrombocytopenia, and hemorrhage, which are typical manifestations in DHF. Under the same treatments, pathophysiological changes in the Nlrp3 inflammasome–deficient mice were notably reduced compared with those in the wild-type mice. These results suggest that the Nlrp3 inflammasome constitutes a potential therapeutic target for treating DENV-induced hemorrhage in DHF.

BackgroundLethal toxin (LT), the major virulence factor produced by Bacillus anthracis, has been shown to suppress the immune system, which is beneficial to the establishment of B. anthracis infections. It has been suggested that the suppression of MEK/MAPK signaling pathways of leukocytes contributes to LT-mediated immunosuppressive effects. However, the involvement of MAPK independent pathways has not been clearly elucidated; nor has the crucial role played by LT in the early stages of infection. Determining whether LT exerts any pathological effects before being enriched to an MEK inhibitory level is an important next step in the furtherance of this field.Methodology/Principal FindingsUsing a cell culture model, we determined that low doses of LT inhibited phagocytosis of macrophages, without influencing MAPK pathways. Consistent low doses of LT significantly suppressed bacterial clearance and enhanced the mortality of mice with bacteremia, without suppressing the MEK1 of splenic and peripheral blood mononuclear cells.Conclusion/SignificanceThese results suggest that LT suppresses the phagocytes in a dose range lower than that required to suppress MEK1 in the early stages of infection.