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John W Semple

Publications and source records attributed to John W Semple.

18 recordsLinked to original sources
PubMed2006

A role for IL-1 receptor antagonist or other cytokines in the acute therapeutic effects of IVIg?

The exact mechanism of action of IVIg in the amelioration of immune thrombocytopenic purpura (ITP) is still unclear. Studies have suggested that IVIg may function through the regulation of cytokines, including interleukin-1 receptor antagonist (IL-1Ra), an inhibitor of phagocytosis. Using a mouse model relevant to ITP, we confirm an increase in mouse serum levels of IL-1Ra after exposure to IVIg, yet a recombinant IL-1Ra did not ameliorate thrombocytopenia. IVIg has also been shown to affect the expression of other regulatory cytokines. We have also recently established that IVIg specifically targets activating FcgammaRs on CD11c+ dendritic cells (DCs) as its primary mechanism of action in the amelioration of murine ITP. Herein, we show that IVIg functions therapeutically in mice lacking specific cytokines or their receptors that can potentially affect DC/macrophage function (IL-1 receptor, IL-4, IL-10, IL-12beta, TNF-alpha, IFN-gamma receptor, MIP-1alpha). This suggests that while IVIg may mediate the release of a variety of cytokines, the cytokines tested do not directly participate in the mechanism of IVIg action.

Animals↗
PubMed2006

Intravenous immunoglobulin inhibits anti-glycoprotein IIb-induced platelet apoptosis in a murine model of immune thrombocytopenia.

We have previously shown that injection of anti-glycoprotein (GP) IIb induces murine immune thrombocytopenia (ITP) and that intravenous immunoglobulin (IVIg) ameliorates ITP. We hypothesise that murine ITP may be associated with platelet apoptosis, which is upregulated by anti-GPIIb and downregulated by IVIg. The current study demonstrated that anti-GPIIb injection induced three critical apoptosis manifestations in platelets: (i) mitochondrial inner transmembrane potential (delta psi m) depolarisation; (ii) caspase-3 activation; and (iii) phosphatidylserine (PS) exposure. IVIg administration inhibited caspase-3 activation and PS exposure, but not delta psi m-depolarisation, in anti-GPIIb-treated platelets, demonstrating that IVIg ameliorates thrombocytopenia concomitantly with inhibiting late, but not early mechanisms of platelet apoptosis.

Animals↗
PubMed2005

A novel murine model of fetal and neonatal alloimmune thrombocytopenia: response to intravenous IgG therapy.

Fetal and neonatal alloimmune thrombo cytopenia (FNAITP) is a life-threatening bleeding disorder caused by maternal antibodies directed against fetal platelet antigens. The immunoreactive epitopes in FNAITP are primarily located in the extracellular regions of the platelet glycoprotein IIIa (beta3 integrin). Here we have established a novel animal model of FNAITP using beta3 integrin-deficient (beta3-/-) mice. We demonstrated first that these mice are immunoresponsive to beta3 integrin; beta3-/- mice transfused with wild-type platelets generated specific anti-beta3 antibodies which were able to induce thrombocytopenia in wild-type mice. Subsequently, beta3-/- female mice (both naive and immunized) were bred with wild-type male mice to recapitulate the features of FNAITP. The titer of generated maternal antibodies correlated with the severity of FNAITP. High titer maternal anti-beta3 anti-bodies caused severe fetal thrombocytopenia, intracranial hemorrhage, and even miscarriage. Furthermore, maternal administration of intravenous immunoglobulin G (IgG) ameliorated FNAITP and down-regulated pathogenic antibodies in both the maternal and fetal circulations.

Animals↗
PubMed2005

Platelet Toll-like receptor expression modulates lipopolysaccharide-induced thrombocytopenia and tumor necrosis factor-alpha production in vivo.

Toll-like receptors (TLRs) play a critical role in stimulating innate immunity by recognizing pathogen-associated molecular patterns (PAMPs) on invading microorganisms. Platelets also play a role in innate immunity, and we studied whether they express TLR. Results show that human and murine platelets variably expressed TLR2, TLR4, and TLR9 by flow cytometry and Western blotting. TLR4 expression was confirmed by demonstrating murine platelet binding to lipopolysaccharide (LPS). Thrombin activation of the platelets significantly enhanced the expression of TLR9, suggesting that at least some TLRs may derive from intracellular compartments. When LPS was administered to LPS-sensitive C3H/HeN and LPS-resistant C3H/HeJ mice, functional TLR4 expression in vivo was shown to be responsible for LPS-induced thrombocytopenia. However, when the C3H/HeN mice were first rendered thrombocytopenic by an antiplatelet antibody and then administered LPS, a significant reduction occurred in their ability to produce TNF-alpha. The decreased cytokine production in the thrombocytopenic mice was restored with platelet transfusion. These results suggest that platelets express various TLRs and that the functional significance of one of these, TLR4, appears to be a role in the modulation of LPS-induced thrombocytopenia and TNF-alpha production. This work implicates platelets as important mediators of innate immune responses against invading microorganisms.

Animals↗
PubMed2005

Autoimmune pathogenesis and autoimmune hemolytic anemia.

Autoimmune hemolytic anemia (AIHA) is an autoimmune disorder in which autoantibodies are directed against an individual's own red blood cells (RBCs), leading to enhanced clearance through Fc receptor (FcR)-mediated phagocytosis. Although there is a large literature relating to clinical aspects of AIHA, relatively little work addresses how IgG autoantibodies are actually produced against RBC autoantigens. This review will first discuss the current understanding of autoimmunity in general and then focus on the knowledge of the immunopathogenic mechanisms responsible for autoantibody production in AIHA. Both human and animal studies will be discussed. Understanding theses mechanism is vital for developing antigen-specific immunotherapies to treat the disease.

Anemia, Hemolytic, Autoimmune↗
PubMed2005

Quality of thrombin produced from the patient's own plasma using the TPD, a new Thrombin-processing Device.

Thrombin derived from bovine sources commonly is used to arrest bleeding during surgical procedures. However, complications such as postoperative hemorrhage can occur because of the development of cross-reactive anti-bovine antibodies that inhibit human coagulation factor V. It would thus be advantageous to develop techniques to generate human thrombin. This study evaluated thrombin produced from human plasma using a new Thrombin-Processing Device (TPD). Plasma was introduced into the TPD, mixed with an ethanol/ CaCl2 reagent, incubated for 1 h, and the harvested thrombin was assayed for activity and the ability to activate platelets by in vitro assays. TPD-produced thrombin activity was found to be 51.8 +/- 12.4 IU/mL (n = 145). TPD-produced thrombin also stimulated P-selectin (CD62) expression (83 +/- 13% of the platelet population) and Annexin V binding (10.3 +/- 2% of the platelet population) on platelets in a similar fashion to commercial thrombin (P-selectin expression: 88 +/- 3%; Annexin-V binding: 11.4 +/- 3%). Compared with CaCl2 and batroxobin, TPD-produced thrombin had a significantly greater ability to activate platelets. TPD-produced thrombin from human plasma has consistent activity and significantly activates platelets and, thus, may have attractive applications such as the production of autologous thrombin for surgical patients.

Blood Loss, Surgical↗
PubMed2004

Inhibition of xenogeneic GVHD by PEN110 treatment of donor human PBMNCs.

BACKGROUND: Development and characterization of methods for preventing transfusion-associated GVHD have utilized in vitro studies with human WBCs and in vivo studies in animal models. The limitation of these assays is that the in vivo GVHD response of treated human WBCs has not been tested directly. STUDY DESIGN AND METHODS: PBMNCs isolated from nonleukoreduced RBC units exposed to gamma irradiation, treated with PEN110 or PBS, were tested for their ability to induce xenogeneic GVHD when injected into severe combined immunodeficient (SCID) mice. RESULTS: These studies showed that the SCID mice injected with PBS-treated PBMNCs developed serum levels of human immunoglobulin that were followed by weight loss and display of ruffled fur characteristic of xenogeneic GVHD in these mice. In contrast, SCID mice injected with PEN110-treated or gamma-irradiated PBMNCs did not exhibit any of these responses. CONCLUSIONS: In these studies PEN110 treatment and gamma irradiation were equally effective at preventing in vivo GVHD responses when the treated cells were injected into SCID recipients. These results are consistent with previous results obtained when these two treatment methods were compared with in vitro studies with PBMNCs and in vivo studies in mouse models.

Animals↗
PubMed2004

Immune responsiveness against allogeneic platelet transfusions is determined by the recipient's major histocompatibility complex class II phenotype.

BACKGROUND: Immunoglobulin G (IgG) anti-platelet (PLT) immunity has been shown to be initiated by indirect allorecognition where recipient T cells recognize donor PLT antigens presented by class II molecules encoded by the major histocompatibility complex (MHC) on recipient antigen-presenting cells. To understand how the recipient's MHC class II molecules may influence PLT alloimmunity, immune responsiveness against transfused PLTs was tested in different mouse strains. STUDY DESIGN AND METHODS: Various inbred and mutant mouse strains were transfused with allogeneic PLTs and IgG donor antibodies were measured by flow cytometry. RESULTS: When recipient mice, expressing both MHC class II I-A and MHC class II I-E molecules, were transfused weekly with allogeneic PLTs, high titers of IgG donor antibodies were generated. In comparison, however, recipient mice expressing only MHC class II I-A molecules had significantly (p < 0.001) reduced IgG antibody responsiveness against PLT transfusions. The low IgG responder status against allogeneic PLT transfusions was rescued in transgenic mice expressing I-E molecules and in mice genetically deficient in either beta2-microglobulin or CD8+ T cells. CONCLUSION: IgG immune responsiveness against allogeneic PLT transfusions is dependent on recipient expression of I-E MHC class II molecules, whereas I-A expression is linked with CD8-mediated suppression of PLT immunity. The data suggest that strategies to modify recipient MHC class II presentation of donor PLT antigens would be effective in eliminating PLT alloimmunity.

Animals↗
PubMed2003

IgG antiplatelet immunity is dependent on an early innate natural killer cell-derived interferon-gamma response that is regulated by CD8+ T cells.

The mechanisms responsible for immunoglobulin G (IgG) immunity against allogeneic platelets are poorly understood. We studied the role that murine recipient CD8+ T and natural killer (NK) cells play in immunity against allogeneic platelets. BALB/c mice were depleted of the cells by cell-specific antibodies, transfused weekly with platelets from C57BL/6 mice, and serum IgG antidonor antibodies were measured by flow cytometry. While allogeneic platelet transfusions into wild-type recipients stimulated IgG antidonor antibodies in all mice by the fifth transfusion, CD8-depleted mice had significantly (P<.001) enhanced antibody production. Isotype analysis revealed that CD8+ T cells suppressed T-helper 2 (Th2)-associated IgG1 but enhanced Th1-associated IgG2a. Compared with wild-type mice, platelet transfusions into CD8-depleted mice stimulated enhanced intracellular interferon (IFN)-gamma production by CD4- lymphocytes within 24 hours after the first transfusion. The early IFN-gamma response correlated with nitric oxide-dependent splenic cytotoxicity (P<.001). In asialo ganglioside monosialic acid 1 (GM1)-depleted mice transfused with allogeneic platelets, the IFN-gamma production, splenic cytotoxicity, and IgG antidonor antibody response were significantly suppressed. These results demonstrate that IgG antiplatelet immunity is dependent on an early NK cell-derived IFN-gamma response that is negatively regulated by CD8+ T cells and suggest that targeting innate NK cell responses may significantly reduce platelet alloimmunization.

Animals↗
PubMed2003

Anti-D initially stimulates an Fc-dependent leukocyte oxidative burst and subsequently suppresses erythrophagocytosis via interleukin-1 receptor antagonist.

Previous results have demonstrated that anti-D therapy in children with chronic auto-immune thrombocytopenic purpura (AITP) induced a significant increase in several pro- and anti-inflammatory plasma cytokines within 2 hours of administration. To investigate the biologic basis of these early in vivo responses, we developed a flow cytometric assay to measure Fc-dependent responses of human peripheral leukocytes with fluorescently labeled and anti-D-opsonized red blood cells (RBCs). When anti-D-opsonized RBCs were incubated with peripheral blood leukocytes, the earliest detectible event observed was a significant oxidative burst in both monocytes (P <.05) and granulocytes (P <.0001), characterized by the production of hydrogen peroxide (H2O2), peroxynitrite (ONOO-), superoxide (O -2), and hydroxyl (OH) by 10 minutes which declined by 1 hour. By 2 hours, the opsonized RBCs were phagocytosed, particularly by granulocytes (P <.001), but the phagocytosis subsequently declined by 6 hours of incubation. The decline in phagocytosis was correlated with a significant production of interleukin-1 receptor antagonist (IL1ra) by both monocytes (P =.036) and granulocytes (P =.0002) within 4 hours. None of these events occurred if the RBCs were coated with anti-D F(ab)'2 fragments. When recombinant IL1ra was titrated into the assay, phagocytosis of the opsonized RBCs was significantly inhibited (P =.002). Taken together, these results suggest that at least one mechanism of action of anti-D is via the production of the anti-inflammatory cytokine IL1ra which can negatively regulate the ability of leukocytes to phagocytose opsonized cells.

Cytokines↗
PubMed2003

T cell and cytokine abnormalities in patients with autoimmune thrombocytopenic purpura.

Autoimmune thrombocytopenic purpura (AITP) is a bleeding disorder in which autoantibodies are directed against an individual's own platelets, leading to enhanced clearance through Fc receptor (R)-mediated phagocytosis by macrophages residing in the reticuloendothelial system, particularly in the spleen. Although the immunopathogenesis of the disease is autoantibody-mediated, there is now substantial evidence that suggest that the antiplatelet autoantibodies are under the control of T helper (Th) cells and the cytokines that they produce. This review will summarize the recent literature regarding abnormal Th cell reactivities and cytokine secretion in AITP. Reviews of the earlier literature regarding cell mediated immunity in chronic AITP have been published [; ]. Understanding the immune mechanisms controlling cell-mediated mechanisms is vital for developing antigen specific immunotherapies to treat the disease.

Autoimmunity↗
PubMed2003

Cellular immune mechanisms in autoimmune thrombocytopenic purpura: An update.

Autoimmune thrombocytopenic purpura (AITP) is a bleeding disorder in which autoantibodies are directed against an individual's own platelets, leading to enhanced clearance through Fc receptor (R)-mediated phagocytosis by macrophages residing in the reticuloendothelial system (RES), particularly in the spleen. The production of IgG autoantibodies is critically dependent on cellular immune mechanisms particularly relating to T cells. We review the recent literature of the cell-mediated immunology of AITP focusing on platelet phenotype, genetics, T-cell reactivities, and cytokine profiles in patients with AITP. Understanding the interaction between these cell-mediated mechanisms is vital for developing antigen specific immunotherapies to treat this autoimmune disease.

Autoantibodies↗
PubMed2003

Pathogenic T-cell responses in patients with autoimmune thrombocytopenic purpura.

Autoimmune thrombocytopenic purpura (AITP) is a bleeding disorder in which autoantibodies are directed against an individual's own platelets, leading to enhanced clearance through Fc receptor (R)-mediated phagocytosis by macrophages residing in the reticuloendothelial system, particularly in the spleen. This review surveys the recent current literature and updates our understanding of the cell-mediated immunology of AITP. It will focus on the relationship between T-cell reactivities and cytokine profiles in patients with AITP. Understanding these cellular immune aspects of AITP is vital for developing antigen-specific immunotherapies to treat the disease.

Cytokines↗
PubMed2002

Gamma-globulins prepared from sera of multiparous women bind anti-HLA antibodies and inhibit an established in vivo human alloimmune response.

It has previously been shown that sera from multiparous women have increased levels of anti-idiotypic antibodies specific for anti-HLA molecules. gamma-Globulins prepared from these sera may be superior to commercial preparations of intravenous gamma-globulin (IVIg) for inhibiting HLA alloimmunization. To test this, F(ab')2 fragments prepared from either commercial IVIg or from the sera of men or multiparous women were coupled to CNBr-Sepharose and tested for their ability to bind F(ab')2 fragments derived from polyspecific anti-HLA sera. As determined by flow cytometry, compared with columns coated with F(ab')2 derived from commercial IVIg or sera from men, columns coated with F(ab')2 prepared from the sera of multiparous women bound significantly more anti-HLA. In addition, intact IgG molecules prepared from the sera of multiparous women significantly neutralized the reactivity of the anti-HLA F(ab')2 fragments. To determine whether the intact IgG molecules or their corresponding F(ab')2 fragments could affect in vivo alloimmunity, they were tested for their ability to inhibit an established IgG human alloimmune response in humanized severe combined immunodeficient (SCID) mice. Compared with commercial IVIg, when intact IgG or F(ab')2 fragments derived from multiparous women were administered to SCID mice making human anti-HLA antibodies, a significant reduction in anti-HLA reactivity was observed. The findings suggest that IgG molecules prepared from the sera of multiparous women have increased anti-idiotypic reactivity against anti-HLA antibodies, which can significantly inhibit an established human IgG alloimmune response in an Fc-independent manner.

Animals↗