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Biomedical subjects

R S Geha

Publications and source records attributed to R S Geha.

At least 37 records · Page 2Linked to original sources
PubMed1999

Effect of intravenous immunoglobulin on steroid consumption in patients with severe asthma: a double-blind, placebo-controlled, randomized trial.

BACKGROUND: There is a significant group of patients with severe asthma who require chronic use of systemic steroids for control of their disease. These patients are at risk for severe side effects from oral steroids. Intravenous immunoglobulin (IVIG) has immunomodulatory properties, and a few open-label trials have suggested its possible benefit in individuals with severe asthma. OBJECTIVE: This study was designed to assess the potential benefit of IVIG as a steroid-sparing agent in patients with severe asthma. METHODS: Thirty-eight immunocompetent steroid-requiring patients with severe asthma were randomly enrolled in a double-blind, placebo-controlled trial of IVIG. RESULTS: Of the 38 patients enrolled, 28 patients completed the study. A significant reduction in oral steroid requirement was observed in both the IVIG-treated (n = 16) and the placebo-treated (n = 12) patients. Further exploration of the results showed that IVIG, but not placebo, had a significant steroid-sparing effect in patients requiring high doses of oral steroids (ie, >2000 mg in the year before the study). Within this subgroup, IVIG treatment (n = 9) resulted in a significant decrease in oral steroid requirement, with a median of 16.4 mg/day during the pretreatment period to 3 mg/day during the treatment phase (P =. 0078). No significant decrease in oral steroid requirement was observed in placebo-treated patients (n = 8) within this subgroup. Objective and subjective parameters of the patients' asthma were unchanged in spite of the steroid tapering achieved in the group treated with IVIG. CONCLUSION: IVIG may be a useful steroid-sparing agent in patients with severe asthma requiring high doses of oral steroids.

Administration, Oral↗
PubMed1999

Structure of the murine TRAF1 gene.

We have cloned, characterized and sequenced the murine TNF Receptor Associated Factor 1 (TRAF1) gene. Restriction mapping and Southern blotting analysis revealed that the TRAF1 gene comprises 10 exons and 9 intervening introns and spreads over 18 kb of genomic DNA. 5'-RACE analysis of the TRAF1 transcript using mRNA from activated spleen B cells revealed several transcription start sites between positions -42 to +4 relative to the 5'end of the murine TRAF1 cDNA sequence. We also isolated and sequenced the 5'-upstream promoter region, which lacks TATA-like and CAAT-like sites but contains GC-rich sequences. Taken together, these results suggest that the TRAF1 gene promoter is a member of the class of Sp-1-dependent promoters. Near the transcription initiation start site we identified three identical decanucleotide repeats (CCAGCCCAGC) which may play a role in the transcriptional regulation of TRAF1 expression. In addition we show that TRAF1 mRNA is not expressed in non-stimulated lymphocytes but can be induced upon activation with different stimuli, including anti-CD3, anti-IgM, anti-CD40 antibodies, LPS, or a combination of phorbol-12-myristate-13-acetate and ionomycin.

Animals↗
PubMed1999

Waltzing with WASP.

Wiskott-Aldrich syndrome (WAS) is an inherited immune deficiency that is marked by eczema, bleeding and recurrent infections. The lymphocytes and platelets of WAS patients display cytoskeletal abnormalities, and their T lymphocytes show a diminished proliferative response to stimulation through the T-cell receptor-CD3 complex (TCR-CD3). The product of the WAS gene, WAS protein (WASP), binds to the small GTPase Cdc42. Small GTPases of the Rho family are crucial for the regulation of the actin-based cytoskeleton. WASP and its relative NWASP might play an important role in regulating the actin cytoskeleton. Since both WASP and NWASP have the potential to bind to multiple proteins, they might serve as a hub to coordinate the redistribution of many cellular signals to the actin cytoskeleton. In this review, the authors discuss the possible role of WASP/NWASP and of the newly described protein WIP, which interacts with WASP and NWASP, in coupling signals from the T-cell receptor to the actin-based cytoskeleton.

Actins↗
PubMed1999

Ku in the cytoplasm associates with CD40 in human B cells and translocates into the nucleus following incubation with IL-4 and anti-CD40 mAb.

CD40 plays a critical role in survival, growth, differentiation, and class switching of B lymphocytes. Although Ku is required for immunoglobulin class switching, how CD40 signal transduction is coupled to Ku is still unknown. Here, we show that CD40 directly interacts with Ku through the membrane-proximal region of cytoplasmic CD40. Ku was confined to the cytoplasm in human primary B cells, and the engagement of CD40 on the B cells cultured in the presence of IL-4 resulted in the dissociation of Ku from CD40, translocation of Ku into the nucleus, and increase in the activity of DNA-dependent protein kinase. These findings indicate that Ku is involved in the CD40 signal transduction pathway and may play an important role in the CD40-mediated events.

Antibodies, Monoclonal↗
PubMed1999

Roles of TH1 and TH2 cytokines in a murine model of allergic dermatitis.

Skin lesions in atopic dermatitis (AD) are characterized by hypertrophy of the dermis and epidermis, infiltration by T cells and eosinophils, and expression of the cytokines IL-4, IL-5, and IFN-gamma. The role of these cytokines in the pathogenesis of AD is not known. We took advantage of a recently described murine model of AD elicited by epicutaneous sensitization with ovalbumin (OVA) (1) and of the availability of mice with targeted deletions of the IL-4, IL-5, and IFN-gamma cytokine genes to assess the role of these cytokines in this model.OVA-sensitized skin from IL-5(-/-) mice had no detectable eosinophils and exhibited decreased epidermal and dermal thickening. Sensitized skin from IL-4(-/-) mice displayed normal thickening of the skin layers but had a drastic reduction in eosinophils and a significant increase in infiltrating T cells. These findings were associated with a reduction in eotaxin mRNA and an increase in mRNA for the T-cell chemokines macrophage inflammatory protein-2 (MIP-2), MIP-1beta, and RANTES. Sensitized skin from IFN-gamma-/- mice was characterized by reduced dermal thickening. These results suggest that both the TH2 cytokines IL-4 and IL-5 and the TH1 cytokine IFN-gamma play important roles in the inflammation and hypertrophy of the skin in AD.

Allergens↗
PubMed1999

SLP-76 deficiency impairs signaling via the high-affinity IgE receptor in mast cells.

SLP-76 is an adapter protein expressed in T cells and myeloid cells that is a substrate for ZAP-70 and Syk. SLP-76-deficient mice exhibit a profound block in T-cell development. We found that although SLP-76 is expressed in mouse mast cells, SLP-76(-/-) mice have normal numbers of mast cells in their skin and bronchi. SLP-76(-/-) mice are resistant to IgE-mediated passive anaphylaxis. SLP-76(-/-) mice sensitized with IgE anti-dinitrophenyl (DNP) and then challenged with DNP-HSA developed only mild and transient tachycardia, failed to increase their plasma histamine level, and all survived the antigen challenge. Bone marrow-derived mast cells (BMMCs) from SLP76(-/-) mice failed to release beta-hexosaminidase and to secrete IL-6 after FcepsilonRI cross-linking. Tyrosine phosphorylation of phospholipase C-gamma1 (but not of Syk) and calcium mobilization in response to IgE cross-linking were reduced in SLP-76-deficient BMMCs. These results suggest that SLP-76 plays an important role in FcepsilonRI-mediated signaling in mast cells.

Adaptor Proteins, Signal Transducing↗
PubMed1998

The role of the CD40 pathway in alloantigen-induced hyporesponsiveness in vivo.

Resting B (rB) cells are known to be incompetent APCs in vitro, which alone can induce specific unresponsiveness to single minor histocompatibility (miH) Ags and, when combined with CD40 pathway blockade, can induce hyporesponsiveness to MHC molecules in vivo. Here we show that anti-CD40 ligand (CD40L) mAb does not prevent the expression of B7-2 on allogeneic rB cells in vivo but did prolong donor-specific cardiac allograft survival. Moreover, pretreatment with professional APCs combined with anti-CD40L mAb induced hyporesponsiveness to alloantigens in vivo. rB cells from CD40 knockout mice were unable to induce unresponsiveness, while graft prolongation was achieved in CD40L knockout recipients pretreated with wild-type rB cells. These data suggest that CD40-CD40L interactions in the recipient play a critical role in the induction of hyporesponsiveness to alloantigens in vivo and that the effect of the CD40 pathway may be independent of its effect on the B7 costimulatory pathway.

Abatacept↗
PubMed1998

Role of JAK3 in CD40-mediated signaling.

CD40 is a member of the tumor necrosis factor receptor family and plays an important role in B-cell survival, growth, differentiation, and isotype switching. Recently, CD40 has been shown to associate with JAK3, a member of the family of Janus Kinases, which are nonreceptor protein kinases involved in intracellular signaling mediated by cytokines and growth factors. To investigate the role of JAK3 in CD40-mediated signaling, we studied the effect of CD40 stimulation on B-cell proliferation, IgE isotype switching, and upregulation of surface expression of CD23, ICAM-1, CD80, and LT-alpha in JAK3-deficient patients. Our studies show that stimulation of B cells with monoclonal antibody to CD40 in the presence of interleukin-4 (IL-4) or IL-13 resulted in similar responses in JAK3-deficient patients and normal controls. This suggests that JAK3 is not essential for CD40-mediated B-cell proliferation, isotype switching, and upregulation of CD23, ICAM-1, CD80, and LT-alpha surface expression.

Antigens, Surface↗
PubMed1998

The Wiskott-Aldrich syndrome protein-interacting protein (WIP) binds to the adaptor protein Nck.

Nck is a ubiquitous adaptor molecule composed of three Src homology 3 (SH3) domains followed by a single SH2 domain. Nck links, via its SH2 domain, tyrosine-phosphorylated receptors to effector proteins that contain SH3-binding proline-rich sequences. In this report, we demonstrate that recombinant Nck precipitates endogenous WIP, a novel proline-rich protein that interacts with the Wiskott-Aldrich syndrome protein (WASP), from BJAB cell lysates. Nck binds through its second SH3 domain to WIP, and Nck binds to WIP at a site (amino acids 321-415) that differs from the WASP-binding site (amino acids 416-488). WIP has been shown to associate with the actin polymerization regulatory protein profilin and to induce actin polymerization and cytoskeletal reorganization in lymphoid cells. We demonstrate the presence of profilin in Nck precipitates suggesting that Nck may couple extracellular signals to the cytoskeleton via its interaction with WIP and profilin.

Actins↗
PubMed1998

Impaired viability and profound block in thymocyte development in mice lacking the adaptor protein SLP-76.

The adaptor protein SLP-76 is expressed in T lymphocytes and myeloid cells and is a substrate for ZAP-70 and Syk. We generated a SLP-76 null mutation in mice by homologous recombination in embryonic stem cells to evaluate the role of SLP-76 in T cell development and activation. SLP-76-deficient mice exhibited subcutaneous and intraperitoneal hemorrhaging and impaired viability. Analysis of lymphoid cells revealed a profound block in thymic development with absence of double-positive CD4+8+ thymocytes and of peripheral T cells. This block could not be overcome by in vivo treatment with anti-CD3. V-D-J rearrangement of the TCRbeta locus was not obviously affected. B cell development was normal. These results indicate that SLP-76 collects all pre-TCR signals that drive the development and expansion of double-positive thymocytes.

Adaptor Proteins, Signal Transducing↗
PubMed1998

Epicutaneous sensitization with protein antigen induces localized allergic dermatitis and hyperresponsiveness to methacholine after single exposure to aerosolized antigen in mice.

Our understanding of the pathogenesis of atopic dermatitis (AD) and its relationship to asthma remains incomplete. Herein, we describe a murine model of epicutaneous (EC) sensitization to the protein allergen, chicken egg albumin, ovalbumin (OVA), which results in a rise in total and OVA-specific serum IgE and leads to the development of a dermatitis characterized by infiltration of CD3(+) T cells, eosinophils, and neutrophils and by local expression of mRNA for the cytokines IL-4, IL-5, and interferon-gamma. A single exposure of the EC sensitized mice to aerosolized OVA induced eosinophilia in the bronchoalveolar lavage fluid and airway hyperresponsiveness to intravenous methacholine as assessed by measurement of pulmonary dynamic compliance (Cdyn). These results suggest a possible role for EC exposure to antigen in atopic dermatitis and in the development of allergic asthma.

Administration, Cutaneous↗
PubMed1998

CD40 ligation and IL-4 use different mechanisms of transcriptional activation of the human lymphotoxin alpha promoter in B cells.

We have previously shown that both CD40 ligation and IL-4 induce lymphotoxin alpha (LT alpha) expression in B cells. We generated a series of truncations of the LT alpha upstream region (-915 to +7 bp) and examined their ability to drive expression of a luciferase (LUC) reporter gene in B cells. The CD40-responsive promoter region of LT alpha was mapped to the region spanning -120 to -52 bp. This region contains an NF-kappa B site (-99 to -89 bp) which was shown to form a complex with nucleoproteins from CD40-stimulated B cells that contained the p50/p65 subunits of NF-kappa B. Mutation of the NF-kappa B site within the -356 to +7 bp region of the LT alpha gene completely abolished its capacity to drive transcription of the LUC gene in response to stimulation with CD40, but not to IL-4. The IL-4-responsive promoter region of LT alpha was mapped to the region spanning -265 to -185 bp. This region contains a site for binding to signal transducers and activators of transcription (STAT) proteins (-197 to -189 bp). This site was shown to form a complex with nucleoproteins from IL-4-stimulated B cells that contained STAT6. Mutation of the STAT site within the -356 to +7 bp region of the LT alpha gene completely abolished its capacity to drive transcription of the LUC gene in response to IL-4, but not to anti-CD40. These results demonstrate that CD40 and IL-4 use distinct mechanisms, namely activation of NF-kappa B and STAT6, respectively, to activate transcription of the LT alpha gene in B cells.

CD40 Antigens↗
PubMed1998

IgE-mediated allergy and desensitization to factor IX in hemophilia B.

BACKGROUND: We describe two patients with factor IX deficiency and high levels of inhibitors to factor IX who developed anaphylaxis to factor IX. OBJECTIVE: The aim of this study was to develop a skin test, RAST, and desensitization protocol for factor IX allergy. METHODS: The patients were evaluated by skin test and RAST to factor IX. They also underwent desensitization to factor IX. RESULTS: Both patients had positive skin test and RAST reactions to factor IX. Control subjects had negative reactions. Both patients were successfully desensitized to factor IX by using two different desensitization protocols. The patients' skin test and RAST reactions to factor IX converted to negative after desensitization. CONCLUSIONS: IgE-mediated reactions to factor IX do occur and may be diagnosed with the use of skin test and RAST. Patients with this type of reaction may be successfully desensitized to factor IX.

Child↗
PubMed1998

The mouse genome contains two expressed intronless retroposed pseudogenes for the sentrin/sumo-1/PIC1 conjugating enzyme Ubc9.

The ubiquitin conjugating (ubc) E2 enzyme ubc-9 conjugates the ubiquitin-like peptide sentrin/SUMO-1/PIC1 to target proteins which include the Fas antigen. We show that the mouse genome contains four copies of the ubc-9 gene. These include a structural ubc-9 gene consisting of seven exons which encode a protein identical to human ubc-9, and three intronless processed pseudogenes. The open reading frames (ORF) of two of the pseudogenes, ubc9-psi1 and ubc9-psi2, correspond to the cDNA of ubc-9 and encode for proteins which differ from ubc9 by three and one amino acid substitutions respectively. The third pseudogene, ubc9-psi3, contains many mutations and stop codons. ubc9-psi1 and ubc9-psi2 are flanked by 5'- and 3'-untranslated (UT) regions homologous to those of the structural ubc-9 gene. Both genes contain a polyA tail and direct repeats at both ends suggesting that they arose by mRNA retroposition. Both ubc9-psi1 and ubc9-psi2 are transcribed into mRNA in murine cells. In contrast to ubc9, the protein products of ubc9-psil and ubc9-psi2 fail to bind Fas and to complement an yeast conditional ubc9 mutant. These results suggest that ubc9-psi1 and ubc9-psi2 encode for proteins that may interact with targets that differ from those recognized by ubc-9.

Amino Acid Sequence↗
PubMed1997

WIP, a protein associated with wiskott-aldrich syndrome protein, induces actin polymerization and redistribution in lymphoid cells.

Wiskott-Aldrich syndrome (WAS) is an X-linked immunodeficiency caused by mutations that affect the WAS protein (WASP) and characterized by cytoskeletal abnormalities in hematopoietic cells. By using the yeast two-hybrid system we have identified a proline-rich WASP-interacting protein (WIP), which coimmunoprecipitated with WASP from lymphocytes. WIP binds to WASP at a site distinct from the Cdc42 binding site and has actin as well as profilin binding motifs. Expression of WIP in human B cells, but not of a WIP truncation mutant that lacks the actin binding motif, increased polymerized actin content and induced the appearance of actin-containing cerebriform projections on the cell surface. These results suggest that WIP plays a role in cortical actin assembly that may be important for lymphocyte function.

Actins↗