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Raif S Geha

Publications and source records attributed to Raif S Geha.

At least 37 records · Page 2Linked to original sources
PubMed2005

COX-2 inhibition enhances the TH2 immune response to epicutaneous sensitization.

BACKGROUND: Mechanical injury to the skin by scratching is an important feature of atopic dermatitis (AD). OBJECTIVE: To investigate the role of COX-2 in allergic skin inflammation elicited by epicutaneous (EC) sensitization via introduction of ovalbumin through shaved tape-stripped skin. METHODS: COX-2 mRNA was measured by quantitative PCR, and COX-2 protein was measured by Western blotting. We investigated the effect of administration of the COX-2 selective inhibitor NS-398 during EC sensitization with ovalbumin in a mouse model of AD characterized by eosinophil skin infiltration, elevated total and antigen specific IgE, and a systemic TH2 response to antigen. We further examined the response of COX-2-deficient mice to EC immunization with ovalbumin. RESULTS: Tape stripping caused a transient increase in skin COX-2 mRNA. In contrast, COX-2 mRNA was not increased after ovalbumin sensitization. Infiltration by eosinophils and expression of IL-4 mRNA in ovalbumin-sensitized skin sites, ovalbumin specific IgE and IgG1 antibody responses, and IL-4 secretion by splenocytes after ovalbumin stimulation were all significantly increased in EC mice that received NS-398. In contrast, ovalbumin specific IgG 2a antibody response and IFN-gamma secretion by splenocytes after ovalbumin stimulation were significantly decreased in these mice. COX-2-deficient mice also exhibited an enhanced systemic TH2 response to EC sensitization. CONCLUSION: These results demonstrate that COX-2 limits the TH2 response to EC sensitization and suggest that COX inhibitors may worsen allergic skin inflammation in patients with AD.

Animals↗
PubMed2005

Defective nuclear translocation of nuclear factor of activated T cells and extracellular signal-regulated kinase underlies deficient IL-2 gene expression in Wiskott-Aldrich syndrome.

BACKGROUND: Proliferation and IL-2 production in response to T-cell receptor ligation are impaired in patients with Wiskott-Aldrich syndrome (WAS). The transcription factors nuclear factor-kappaB (NF-kappaB), nuclear factor of activated T cells (NF-AT), and activating protein-1 (AP-1) play a critical role in IL-2 gene expression. OBJECTIVE: To investigate the mechanisms of impaired IL-2 production after T-cell receptor ligation in T cells deficient in WAS protein (WASP). METHODS: T cells from WASP-/- mice were stimulated with anti-CD3 and anti-CD28. Nuclear NF-kappaB, NF-AT, and AP-1 DNA-binding activity was examined by electroshift mobility assay. NF-ATp dephosphorylation and nuclear localization were examined by Western blot and indirect immunofluorescence. Phosphorylation of the mitogen-activated protein kinases Erk and Jnk, and of their nuclear substrates Elk-1 and c-Jun, was examined by Western blot. Expression of mRNA for IL-2 and the NF-kappaB-dependent gene A20 and of the AP-1 components c-fos and c-Jun was examined by quantitative RT-PCR. RESULTS: Nuclear translocation and activity of NF-kappaB were normal in T cells from WASP-/- mice. In contrast, NF-ATp dephosphorylation and nuclear localization, nuclear AP-1 binding activity, and expression of c-fos, but not c-Jun, were all impaired. Phosphorylation of Jnk, c-Jun, and Erk were normal. However, nuclear translocation of phosphorylated Erk and phosphorylation of its nuclear substrate Elk1, which activates the c-fos promoter, were impaired. CONCLUSION: These results suggest that WASP is essential for NF-ATp activation, and for nuclear translocation of p-Erk, Elk1 phosphorylation, and c-fos gene expression in T cells. These defects underlie defective IL-2 expression and T-cell proliferation in WAS.

Active Transport, Cell Nucleus↗
PubMed2005

Human disease resulting from gene mutations that interfere with appropriate nuclear factor-kappaB activation.

The nuclear factor (NF)-kappaB family of transcription factors serves vital roles in a wide array of cell functions. An increasing number of human genetic lesions that result in defined disease entities are linked to inappropriate activation of NF-kappaB. The resulting aberrant NF-kappaB function can lead to cellular defects that ultimately impair normal developmental processes, host immune defenses, or both. Molecular defects that lie upstream in cell-signaling pathways and rely upon NF-kappaB activation tend to give a more specific phenotype, whereas those closer to the actual NF-kappaB proteins have broader defects. A detailed study of these diseases can provide insight into the biochemistry of NF-kappaB activation as well as the role of NF-kappaB in human health.

Genetic Diseases, Inborn↗
PubMed2004

RIP links TLR4 to Akt and is essential for cell survival in response to LPS stimulation.

Receptor-interacting protein (RIP) has been reported to associate with tumor necrosis-associated factor (TRAF)2 and TRAF6. Since TRAF2 and TRAF6 play important roles in CD40 signaling and TRAF6 plays an important role in TLR4 signaling, we examined the role of RIP in signaling via CD40 and TLR4. Splenocytes from RIP(-/-) mice proliferated and underwent isotype switching normally in response to anti-CD40-IL-4 but completely failed to do so in response to LPS-IL-4. However, they normally up-regulated TNF-alpha and IL-6 gene expression and CD54 and CD86 surface expression after LPS stimulation. RIP(-/-) splenocytes exhibited increased apoptosis and impaired Akt phosphorylation after LPS stimulation. These results suggest that RIP is essential for cell survival after TLR4 signaling and links TLR4 to the phosphatidylinositol 3 kinase-Akt pathway.

Animals↗
PubMed2004

Impaired IgA class switching in APRIL-deficient mice.

The tumor necrosis factor (TNF) family member APRIL binds to the receptors BCMA on B cells and TACI on B and T cells. To investigate the role of APRIL in immunity, we generated APRIL-deficient mice. APRIL(-/-) mice have normal T and B lymphocyte development, normal T and B cell proliferation in vitro, but increased numbers of CD44(hi)CD62L(lo) CD4(+) effector/memory T cells and increased IgG responses to T-dependent antigens. Serum IgA levels were significantly decreased, and serum IgA antibody responses to mucosal immunization with TD antigens and to type 1 T-independent antigens were impaired in APRIL(-/-) mice. APRIL by itself induced IgA as well as IgG1 isotype switching in CD40-deficient IgM(+)IgD(+) sorted B cells. These results suggest that APRIL down-regulates T cell-dependent antibody responses and promotes IgA class switching.

Animals↗
PubMed2004

WIP regulates signaling via the high affinity receptor for immunoglobulin E in mast cells.

Wiskott-Aldrich syndrome protein-interacting protein (WIP) stabilizes actin filaments and is important for immunoreceptor-mediated signal transduction leading to actin cytoskeleton rearrangement in T and B cells. Here we report a role for WIP in signaling pathways downstream of the high affinity receptor for immunoglobulin (Ig)E (FcepsilonRI) in mast cells. WIP-deficient bone marrow-derived mast cells (BMMCs) were impaired in their capacity to degranulate and secrete interleukin 6 after FcepsilonRI ligation. Calcium mobilization, phosphorylation of Syk, phospholipase C-g2, and c-Jun NH2-terminal kinase were markedly decreased in WIP-deficient BMMCs. WIP was found to associate with Syk after FcepsilonRI ligation and to inhibit Syk degradation as evidenced by markedly diminished Syk levels in WIP-deficient BMMCs. WIP-deficient BMMCs exhibited no apparent defect in their subcortical actin network and were normal in their ability to form protrusions when exposed to an IgE-coated surface. However, the kinetics of actin changes and the cell shape changes that follow FcepsilonRI signaling were altered in WIP-deficient BMMCs. These results suggest that WIP regulates FcepsilonRI-mediated mast cell activation by regulating Syk levels and actin cytoskeleton rearrangement.

Actins↗
PubMed2004

Characteristics of mycobacterial infection in patients with immunodeficiency and nuclear factor-kappaB essential modulator mutation, with or without ectodermal dysplasia.

Hypomorphic mutations of the nuclear factor kappaB essential modulator gene cause ectodermal dysplasia and immunodeficiency. Affected patients have increased susceptibility to mycobacterial disease including cutaneous manifestations. We describe clinical and histopathologic characteristics of 5 patients with nuclear factor kappaB essential modulator gene mutations and mycobacterial infections, two of whom had mycobacterial cutaneous infections.

Adolescent↗
PubMed2004

The presentation and natural history of immunodeficiency caused by nuclear factor kappaB essential modulator mutation.

BACKGROUND: An increasing number of rare genetic defects are associated with immunodeficiency and impaired ability to activate gene transcription through nuclear factor (NF) kappaB. Hypomorphic mutations in the NFkappaB essential modulator (NEMO) impair NFkappaB function and are linked to both immunodeficiency and ectodermal dysplasia (ED), as well as susceptibility to atypical mycobacterial infections. OBJECTIVE: We sought to investigate the clinical and immunologic natural history of patients with NEMO mutation with immunodeficiency (NEMO-ID). METHODS: Patients with severe bacterial infection and ED or unexplained mycobacterial sensitivity were evaluated for NEMO mutation. Laboratory investigations and clinical data were retrospectively and prospectively accumulated and reviewed. RESULTS: We have given a diagnosis of NEMO-ID to 7 boys; 6 had ED, and 5 had gene mutations in the 10th exon of NEMO. Our resulting estimated incidence of NEMO-ID is 1:250,000 live male births. All patients had serious pyogenic bacterial illnesses early in life, and the median age of first infection was 8.1 months. Most boys had mycobacterial disease (median age, 84 months), and a minority had herpesviral infections. Initial immunologic assessments showed hypogammaglobulinemia (median IgG, 170 mg/dL) with variable IgM (median, 41 mg/dL) and IgA (median, 143 mg/dL) levels. Two patients had increased IgM levels, and 5 had increased IgA levels. All patients evaluated had normal lymphocyte subsets with impaired proliferative responses, specific antibody production, and natural killer cell function. Two patients died from complications of mycobacterial disease (ages 21 and 33 months). CONCLUSION: NEMO-ID is a combined immunodeficiency with early susceptibility to pyogenic bacteria and later susceptibility to mycobacterial infection. Specific features of particular NEMO mutations in these patients provide insight into the role of this gene in immune function.

Agammaglobulinemia↗
PubMed2004

Human nuclear factor kappa B essential modulator mutation can result in immunodeficiency without ectodermal dysplasia.

BACKGROUND: Many receptors rely on the appropriate activation of nuclear factor (NF) kappa B to induce cellular function. This process depends critically on the phosphorylation of the inhibitor of NF-kappa B (I kappa B) by the I kappa B kinase. This targets I kappa B for ubiquitination and degradation, allowing NF-kappa B to translocate to the nucleus, where it can direct transcription. Hypomorphic human mutations affecting one I kappa B kinase component, the NF-kappa B essential modulator (NEMO), result in impaired signaling from receptors required for ectodermal development and immune function. Male subjects with these mutant NEMO molecules have an X-linked syndrome known as ectodermal dysplasia with immunodeficiency, which is characterized by severe infections, with herpesviruses, bacteria, and mycobacterial susceptibility. OBJECTIVE: We sought to genetically and biochemically characterize a patient with a mutant NEMO molecule without ectodermal abnormalities. METHODS: We evaluated NEMO in a patient who had immunodeficiency and atypical mycobacterial infection but normal ectoderm. RESULTS: We identified a novel NEMO mutant causing immunodeficiency without ectodermal dysplasia. The mutation, which altered the exon 9 splice site, was present in cells of ectodermal and hematopoetic origin and resulted in a heterogeneous mixture of mutant and wild-type cDNA species. Immunologic function was variably impaired, with reduced CD40-induced B-cell proliferation, partially reduced NF-kappa B p65 nuclear translocation, and variable Toll-like receptor-induced TNF production. This variability might be explained by an inconsistent ratio of mutant to wild-type NEMO. The lack of any ectodermal phenotype, however, suggested a separation in the hematopoetic and ectodermal function of NEMO that leads to NF-kappa B activation. CONCLUSION: Mutation of the gene encoding NEMO can result in immunodeficiency without ectodermal dysplasia.

Adolescent↗
PubMed2004

Induction of activation-induced cytidine deaminase gene expression by IL-4 and CD40 ligation is dependent on STAT6 and NFkappaB.

Activation-induced cytidine deaminase (AID) is an inducible gene that plays an important role in class switch recombination, somatic hypermutation and gene conversion in B cells. We examined the regulation of AID gene expression in human and mouse B cells by IL-4 and CD40 ligation. IL-4 by itself and, to a much lesser extent, CD40 ligation induced AID mRNA expression in primary B cells. The two stimuli strongly synergized in inducing AID mRNA and protein expression. IL-4 induced STAT6 binding to a site in the 5' upstream region of the AID gene, while CD40 ligation induced NFkappaB binding to two sites in that region. B cells from STAT6-/- mice failed to up-regulate AID in response to IL-4, while B cells from p50-/- mice were impaired in their ability to up-regulate AID in response to CD40 ligation and IL-4. These results suggest that signals delivered via CD40 that activate NFkappaB synergize with signals delivered via the IL-4 receptor that activate STAT6 to induce optimal AID gene expression.

Animals↗
PubMed2004

Erk/Src phosphorylation of cortactin acts as a switch on-switch off mechanism that controls its ability to activate N-WASP.

The Arp2/3 complex can be independently activated to initiate actin polymerization by the VCA domain of WASP family members and by the acidic N-terminal and F-actin-binding repeat region of cortactin, which possesses a C-terminal SH3 domain. Cortactin is a target for phosphorylation by Src tyrosine kinases and by serine/threonine kinases that include Erk. Here we demonstrate that cortactin binds N-WASP and WASP via its SH3 domain, induces in vitro N-WASP-mediated actin polymerization, and colocalizes with N-WASP and WASP at sites of active actin polymerization. Erk phosphorylation and a mimicking S405,418D double mutation enhanced cortactin binding and activation of N-WASP. In contrast, Src phosphorylation inhibited the ability of cortactin previously phosphorylated by Erk, and that of S405,418D double mutant cortactin, to bind and activate N-WASP. Furthermore, Y-->D mutation of three tyrosine residues targeted by Src (Y421, Y466, and Y482) inhibited the ability of S405,418D cortactin to activate N-WASP. We propose that Erk phosphorylation liberates the SH3 domain of cortactin from intramolecular interactions with proline-rich regions, causing it to synergize with WASP and N-WASP in activating the Arp2/3 complex, and that Src phosphorylation terminates cortactin activation of N-WASP and WASP.

Actin-Related Protein 2↗
PubMed2004

The anaphylatoxin C3a downregulates the Th2 response to epicutaneously introduced antigen.

Mechanical injury to the skin results in activation of the complement component C3 and release of the anaphylatoxin C3a. C3a binds to a seven-transmembrane G protein-coupled receptor, C3aR. We used C3aR(-/-) mice to examine the role of C3a in a mouse model of allergic inflammation induced by epicutaneous sensitization with OVA. C3aR(-/-) mice exhibited an exaggerated Th2 response to epicutaneous but not to intraperitoneal sensitization with OVA, as evidenced by significantly elevated levels of serum OVA-specific IgG1 and significantly increased secretion of the Th2 cytokines IL-4, IL-5, and IL-10 by antigen-stimulated splenocytes. Presentation of OVA peptide by C3aR(-/-) APCs caused significantly more IL-4 and IL-5 secretion by T cells from OVA-T cell receptor (OVA-TCR) transgenic mice compared with presentation by WT APCs. C3a inhibited the ability of splenocytes, but not of highly purified T cells, to secrete Th2 cytokines in response to TCR ligation. This inhibition was mediated by IL-12 secreted by APCs in response to C3a. These results suggest that C3a-C3aR interactions inhibit the ability of APCs to drive Th2 cell differentiation in response to epicutaneously introduced antigen and may have important implications for allergic skin diseases.

Anaphylatoxins↗
PubMed2003

The mature activating natural killer cell immunologic synapse is formed in distinct stages.

Natural killer (NK) cells form a structure at their interface with a susceptible target cell called the activating NK cell immunologic synapse (NKIS). The mature activating NKIS contains a central and peripheral supramolecular activation cluster (SMAC), and includes polarized surface receptors, filamentous actin (F-actin) and perforin. Evaluation of the NKIS in human NK cells revealed CD2, CD11a, CD11b and F-actin in the peripheral SMAC (pSMAC) with perforin in the central SMAC. The accumulation of F-actin and surface receptors was rapid and depended on Wiskott-Aldrich syndrome protein-driven actin polymerization. The accumulation at and arrangement of these molecules in the pSMAC was not affected by microtubule depolymerization. The polarization of perforin, however was slower and required intact actin, Wiskott-Aldrich syndrome protein, and microtubule function. Thus the process of CD2, CD11a, CD11b, and F-actin accumulation in the pSMAC and perforin accumulation in the central SMAC of the NKIS are sequential processes with distinct cytoskeletal requirements.

Actins↗
PubMed2003

Targeted inactivation of the IL-4 receptor alpha chain I4R motif promotes allergic airway inflammation.

The insulin/interleukin-4 (IL-4) receptor (I4R) motif mediates the association of insulin receptor substrate (IRS)-2 with the interleukin-4 (IL-4)Ralpha chain and transduces mitogenic signals in response to IL-4. Its physiological functions were analyzed in mice with a germline point mutation that changed the motif's effector tyrosine residue into phenylalanine (Y500F). The Y500F mutation abrogated IRS-2 phosphorylation and impaired IL-4-induced CD4+ T lymphocyte proliferation but left unperturbed Stat6 activation, up-regulation of IL-4-responsive gene products, and Th cell differentiation under Th2 polarizing conditions. However, in vivo the Y500F mutation was associated with increased allergen-induced IgE production, airway responsiveness, tissue eosinophilia, and mucus production. These results define an important role for the I4R motif in regulating allergic inflammation.

Animals↗
PubMed2003

Disseminated varicella infection due to the vaccine strain of varicella-zoster virus, in a patient with a novel deficiency in natural killer T cells.

An 11-year-old girl presented with a papulovesicular rash and severe respiratory distress 5 weeks after receiving varicella vaccine. Restriction fragment length-polymorphism analysis of virus isolated from an endotracheal-tube aspirate and from bronchoalveolar lavage revealed that this patient's illness was due to the Oka vaccine strain of varicella. An extensive immunologic analysis failed to identify a known diagnostic entity to explain her susceptibility to this attenuated vaccine strain. Analysis of her lymphocytes on separate occasions, months after recovery from her illness, revealed a profound deficiency of natural killer T (NKT) cells and of NKT-cell activity, suggesting that NKT cells contribute to host defense against varicella virus.

Antigens, Viral↗