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Biomedical subjects

H D Ochs

Publications and source records attributed to H D Ochs.

At least 91 records · Page 5Linked to original sources
PubMed1997

BTKbase, mutation database for X-linked agammaglobulinemia (XLA)

X-linked agammaglobulinemia (XLA) is an immunodeficiency caused by mutations in the gene coding for Bruton's agammaglobulinemia tyrosine kinase (BTK). A database (BTKbase) of BTK mutations has been compiled and the recent update lists 368 entries from 318 unrelated families showing 228 unique molecular events. In addition to mutations the database lists also some polymorphisms and site-directed mutations. Each patient is given a unique patient identity number (PIN). Information is provided regarding the phenotype including symptoms. Mutations in all the five domains of BTK have been noticed to cause the disease, the most common event being missense mutations. The mutations appear almost uniformly throughout the molecule and frequently affect CpG sites forming arginine residues. These hot spots have generally pyrimidines 5'and purines 3'to the mutated cytosine. A decreased frequency of missense mutations was found in the TH, SH3 and the upper lobe of the kinase domain. The putative structural implications of all the missense mutations are given in the database showing 228 unique molecular events, including a novel missense mutation causing an R28C substitution as previously seen in the Xid mouse.

Agammaglobulinaemia Tyrosine Kinase↗
PubMed1997

Defective antigen-induced lymphocyte proliferation in the X-linked hyper-IgM syndrome.

We examined T-cell proliferation in five patients with X-linked hyper-IgM syndrome (XHIM), using a panel of antigens and lectins. All patients had impaired antigen-induced proliferation, whereas their lectin responses were normal. Thus, in addition to severely depressed antibody responses, patients with XHIM have a defect in antigen-specific T-cell proliferation, which may explain their susceptibility to pathogens such as Pneumocystis carinii.

Antigens↗
PubMed1997

The molecular basis and treatment of primary immunodeficiency disorders.

Over the past decade, a number of important advances have been made in the molecular characterization and the treatment of the primary immunodeficiency disorders. These advances include identification of the abnormal genes responsible for such syndromes as X-linked severe combined immune deficiency, several forms of autosomal severe combined immune deficiency, X-linked and autosomal agammaglobulinemia, Wiskott-Aldrich syndrome, and other primary immunodeficiency disorders. In the past year, the biologic functions of the abnormal gene products responsible for these syndromes have been better defined, and new molecular defects that lead to primary immunodeficiency disorders have also been reported. This better understanding of the molecular basis of the primary immunodeficiency disorders has led to improvement of established therapies, such as gene product replacement and stem cell transplants, and to new treatment strategies, such as gene therapy.

Agammaglobulinemia↗
PubMed1997

Tyrosine kinase signaling regulates Wiskott-Aldrich syndrome protein function, which is essential for megakaryocyte differentiation.

Platelets are produced from megakaryocytes differentiated from megakaryoblasts, but the differentiation mechanism still remains unknown. Here, we demonstrate that a tyrosine kinase signaling regulates Wiskott-Aldrich syndrome protein (WASP), which is essential for megakaryocyte differentiation. MEG-01 megakaryoblastic cells differentiate into large multinucleated megakaryocyte-like cells characterized by microvesicle formation with a protein kinase C (PKC) activator, 12-O-tetradecanoylphorbol 13-acetate. With parallel to the differentiation, WASP begins to accumulate at microvesicles with actin filaments and associates with tyrosine-phosphorylated Shc, the phosphorylation of which is induced. Moreover, a tyrosine kinase inhibitor, herbimycin A, blocked not only phosphorylation of Shc but also microvesicle formation without affecting cell enlargement and multinucleation, whereas a PKC inhibitor, H-7, completely inhibited all these processes. Because WASP also binds to Ash/Grb2 SH3 domains and the association of Ash/Grb2 and Shc is induced by 12-O-tetradecanoylphorbol 13-acetate treatment, a signaling pathway, PKC-tyrosine kinase-Shc-Ash/Grb2-WASP, is suggested for regulating megakaryocyte differentiation. In addition, WASP antisense oligonucleotide treatment abolishes both microvesicle formation and gathering of actin filaments. These data clearly show that WASP controls the assembly of actin filaments required for microvesicle formation downstream of PKC-tyrosine kinase.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1996

BTKbase, mutation database for X-linked agammaglobulinemia (XLA).

X-linked agammaglobulinemia (XLA) is an immunodeficiency caused by mutations in the gene coding for Bruton's agammaglobulinemia tyrosine kinase (BTK). A database (BTKbase) of BTK mutations has been compiled and the recent update lists 225 entries from 189 unrelated families showing 148 unique molecular events. Each patient is given a unique patient identity number (PIN). Information is included regarding the phenotype including symptoms. Mutations in all the five domains of BTK have been noticed to cause the disease, the most common event being missense mutations. The mutations appear almost uniformly throughout the molecule and frequently affect CpG sites forming arginine residues. A decreased frequency of missense mutations was found in the TH, SH3 and upper lobe of the kinase domain. The putative structural implications of all the missense mutations are given in the database.

Agammaglobulinemia↗
PubMed1996

Classification of mutations in the human CD40 ligand, gp39, that are associated with X-linked hyper IgM syndrome.

The interaction between the T cell activation antigen gp39 and CD40, its receptor CD40 on B cells, plays a critical role in the regulation of humoral immune responses. Using a detailed three-dimensional model of the gp39 extracellular region, we have analyzed 20 mutations in gp39 that were, with one exception, isolated from patients with X-linked hyper IgM (XHIM) syndrome. On the basis of this analysis, the mutations were classified according to their predicted locations and effects. Twelve mutations are thought to compromise the gp39 structure by affecting interactions in hydrophobic core regions or at monomer interfaces, whereas seven others map closely to gp39 residues important for interaction with CD40. The latter mutations may thus, directly or indirectly, interfere with CD40 binding. One naturally occurring mutant whose carrier displays normal immune responses maps to a solvent-exposed position in a loop region of the molecule.

CD40 Antigens↗
PubMed1996

Humoral immunity in steroid-dependent children with asthma and hypogammaglobulinemia.

OBJECTIVE: To determine primary and secondary antibody responses in children with hypogammaglobulinemia attributed to corticosteroid use. RESULTS: In seven patients with steroid-dependent asthma and significant hypogammaglobulinemia (IgG concentration, 275 to 443 mg/dl), antibody responses to protein and polysaccharide antigens were shown to be normal, as were primary and secondary responses to a neoantigen, bacteriophage phi X174. CONCLUSIONS: Patients with asthma, and with hypogammaglobulinemia resulting from steroid therapy, have normal humoral immunity, and immunoglobulin replacement therapy is not indicated.

Adolescent↗
PubMed1996

X-linked agammaglobulinemia. A clinical and molecular analysis.

X-linked agammaglobulinemia (XLA), characterized by a profound deficiency of B lymphocytes due to an arrest in B lymphocyte development, is caused by mutations in the gene encoding Btk (Bruton tyrosine kinase). The BTK gene has been cloned and the genomic organization determined. BTK codes for 19 exons and is expressed in all hematopoietic cell lineages but is selectively down-regulated in T lymphocytes and plasma cells. The different Btk domains include PH, TH, SH3, SH2, and the kinase (SH1) domains. Btk, a cytoplasmic protein tyrosine kinase, is involved in cell signaling, although the precise pathway remains elusive. Mutation analysis has been performed in 236 families representing 282 patients. Mutations are scattered throughout the gene and consist of missense, nonsense, and splice site mutations as well as deletions and insertions. The major consequence of nonfunctional Btk appears to be a delay or block of the development of pro-B cells to pre-B cells and then to mature lymphocytes. Because IgG is actively transported across the placenta, affected newborns have normal levels of serum IgG at birth followed by gradually decreasing IgG levels and development of hypogammaglobulinemia and increased susceptibility to infections. Bacterial infections are the most common clinical manifestation. Resistance to viral infection is intact, except for an unusual susceptibility to infections with enteroviruses that may result in vaccine-related paralytic poliomyelitis or a dermatomyositis-meningoencephalitis syndrome. The diagnosis of XLA is based on the presence of lymphoid hypoplasia, markedly reduced serum levels of all 3 major classes of immunoglobulins, failure to make antibody to antigenic stimulation, and almost complete absence of B lymphocytes in the peripheral blood. Carrier detection and prenatal diagnosis are possible. The prophylactic infusion of high-dose intravenous immunoglobulin (IVIG) and the use of antibiotics have markedly improved the long-term prognosis of patients with XLA.

Agammaglobulinaemia Tyrosine Kinase↗
PubMed1996

Effect of interleukin-10 on anti-CD40- and interleukin-4-induced immunoglobulin E production by human lymphocytes.

We studied the effect of IL-10 on the in vitro synthesis of IgE and IgG by human peripheral blood mononuclear cells (PBMC) following stimulation with anti-CD40 monoclonal antibody and IL-4. Anti-CD40- and IL-4-stimulated PBMC showed an increase in IL-10 synthesis together with increases in IgE and IgG production. Addition of anti-IL-10 antibody to this system suppressed IgE as well as IgG production without affecting the proliferation of PBMC. Addition of IL-10 enhanced IgE and IgG production if PBMC were activated with anti-CD40 and IL-4. PBMC costimulated with anti-CD40, IL-4 and IL-10 showed a remarkable increase in IL-6 production, but had no effect on IFN-gamma production. Addition of IL-10 to purified human tonsillar B cells stimulated with anti-CD40 and IL-4 enhanced B cell proliferation and IgG production, but not IgE production. These results suggest that IL-10 accelerates IgE production by anti-CD40- and IL-4-stimulated PBMC by enhancing IL-6 production through activation of T lymphocytes.

Adult↗
PubMed1996

Immune deficiency in SCID mice.

Since the discovery of SCID mice in 1983, numerous studies utilizing these mice were carried out. These investigations can be classified into two major groups. First, the analysis of the immune defect has revealed defective V(D)J recombination and defective DNA double-strand break repair, and has lead to the identification of the candidate gene for SCID mice. Second, the use of SCID mice to explore ways to introduce a murine or xenogeneic immune system into SCID mice by taking advantage of the immune deficiency of the mice has provided an animal model to examine the in vivo function of transferred human or murine immune cells. In this review, we summarize the recent advances made in these two areas of SCID mouse research.

Animals↗
PubMed1996

A high frequency of distinct ATM gene mutations in ataxia-telangiectasia.

The clinical features of the autosomal recessive disorder ataxia-telangiectasia (AT) include a progressive cerebellar ataxia, hypersensitivity to ionizing radiation, and an increased susceptibility to malignancies. Epidemiological studies have suggested that AT heterozygotes may also be at increased risk for malignancy, possibly as a consequence of radiation exposure. A gene mutated in AT patients (ATM) has recently been isolated, making mutation screening in both patients and the general population possible. Because of the relatively large size of the ATM gene, the design of screening programs will depend on the types and distribution of mutations in the general population. In this report, we describe 30 mutations identified in a panel of unrelated AT patients and controls. Twenty-five of the 30 were distinct, and most patients were compound heterozygotes. The most frequently detected mutation was found in three different families and had previously been reported in five others. This corresponds to a frequency of 8% of all reported ATM mutations. Twenty-two of the alterations observed would be predicted to lead to protein truncation at sites scattered throughout the molecule. Two fibroblast cell lines, which displayed normal responses to ionizing radiation, also proved to be heterozygous for truncation mutations of ATM. These observations suggest that the carrier frequency of ATM mutations may be sufficiently high to make population screening practical. However, such screening may need to be done prospectively, that is, by searching for new mutations rather than by screening for just those already identified in AT families.

Ataxia Telangiectasia↗
PubMed1996

Serum Gm allotype levels in common variable immunodeficiency: preponderance of homozygous G2m(",") on IGHCG2.

Common variable immunodeficiency (CVI) is one of the most frequent primary immunodeficiency diseases, characterized by defective antibody formation and associated with chronic sinopulmonary infections, autoimmunity and malignancies. The genes for the constant heavy chains of IgG are located on chromosome 14 and were further studied by identifying allelic, alternative Gm allotypes. These were defined by different epitopes for three of the IgG subclasses, G1m(a) and G1m(f) for IgG1, G2m(n) and G2m(") for IgG2 and G3m(g) and G3m(b) for IgG3. A sensitive competitive ELISA method for quantitation of the Gm allotypes G1m(a), G1m(f), G2m(n) and G3m(b) were used together with radial immunodiffusion IgG subclass quantitation. The dominating number of 25 of 33 patients (p < 0.001) expressed the homozygous G2m(",") allotype on IGHCG2 in combination with homozygous or heterozygous Gm allotypes on IGHCG1 and IGHCG3, namely Gm(f,f;",";b,b), Gm(a,a;",";g,g) and Gm(f,a;",";b,g). Studies of Gm allotype quantities revealed a progressive sequential impediment of the programmed cascade for downstream IGHCG gene rearrangements. According to the order of the IGHCG genes, the G3m allotype levels from the IGHCG3 were often normal, and G1m allotype levels from IGHCG1 were suppressed; G1m(a) was suppressed more than G1m(f), and most suppressed were G2m allotype levels from IGHCG2, both G2m(n) and G2m("). The susceptibility of CVI is associated to G2m(",") expression from the IGHCG2 locus on chromosome 14, which has also been found in IgA IgG subclass deficiency, conditions known among first-degree relatives.

Adult↗
PubMed1995

The Wiskott-Aldrich syndrome and X-linked congenital thrombocytopenia are caused by mutations of the same gene.

The Wiskott-Aldrich syndrome (WAS) is an X-linked recessive disorder characterized by thrombocytopenia, small platelets, eczema, recurrent infections, and immunodeficiency. Besides the classic WAS phenotype, there is a group of patients with congenital X-linked thrombocytopenia (XLT) who have small platelets but only transient eczema, if any, and minimal immune deficiency. Because the gene responsible for WAS has been sequenced, it was possible to correlate the WAS phenotypes with WAS gene mutations. Using a fingerprinting screening technique, we determined the approximate location of the mutation in 13 unrelated WAS patients with mild to severe clinical symptoms. Direct sequence analysis of cDNA and genomic DNA obtained from patient-derived cell lines showed 12 unique mutations distributed throughout the WAS gene, including insertions, deletions, and point mutations resulting in amino acid substitutions, termination, exon skipping, or splicing defects. Of 4 unrelated patients with the XLT phenotype, 3 had missense mutations affecting exon 2 and 1 had a splice-site mutation affecting exon 9. Patients with classic WAS had more complex mutations, resulting in termination codons, frameshift, and early termination. These findings provide direct evidence that XLT and WAS are caused by mutations of the same gene and suggest that severe clinical phenotypes are associated with complex mutations.

Base Sequence↗
PubMed1995

Characterization of B-cell lines established from two X-linked severe combined immunodeficiency patients: interleukin-15 binds to the B cells but is not internalized efficiently.

X-linked severe combined immunodeficiency (XSCID) is characterized by absent or profoundly reduced numbers of T cells and normal numbers of B cells in the circulation. Affected patients have mutations of the interleukin-2 (IL-2) receptor gamma chain gene. Using Epstein-Barr virus-transformed B-lymphoblastoid cell lines (B-LCLs) established from two unrelated XSCID patients, we could show that neither expressed the IL-2 receptor gamma chain on the cell surface. A novel cytokine IL-15, which has biologic activities similar to those of IL-2, could bind to the XSCID B-LCLs in the absence of the gamma chain, although both the beta and gamma chains of the human IL-2 receptor were previously shown to be required for IL-15 binding by transfected COS cells. Furthermore, a significant reduction and delay of IL-15 internalization by B lymphoblasts from XSCID patients was observed when compared with that of normal control B-LCLs. These results show the existence of a novel IL-15-specific receptor component that contributes to IL-15 binding but is insufficient for IL-15 internalization in the absence of the IL-2 receptor gamma chain.

B-Lymphocytes↗
PubMed1995

Identification of residues on CD40 and its ligand which are critical for the receptor-ligand interaction.

Interactions between gp39 (CD40L, TRAP, T-BAM) on activated T cells and CD40 on antigen-presenting cells play an important role in regulating antibody production by B cells, cytokine production by monocytes, and other immune responses which require T cell "help". Using structure-based sequence alignments, a molecular model of gp39, site-directed mutagenesis, and receptor-ligand binding assays, we have identified CD40 and gp39 surface residues which are important for receptor-ligand binding. Binding studies with CD40 or gp39 proteins containing single and double amino acid substitutions showed that CD40 residues Y82, D84, and N86 are involved in gp39 binding, while gp39 residues K143 and Y145 are important for CD40 binding. Analysis of the location of amino acid substitutions in the naturally occurring gp39 mutants expressed by the X-linked hyper-IgM (X-HIM) patients studied to date indicated the E129/G substitution found in the S128/R-E129/G double mutant affects a solvent-accessible residue which might participate in CD40/gp39 binding. Binding studies with E129/G and E129/A gp39 point mutants showed that this residue does not contribute directly to CD40/gp39 binding but that its substitution with a glycine disrupts the gp39 structure. Comparison of the gp39 and CD40 residues involved in receptor-ligand contacts with those previously identified as playing an important role in TNF-beta/TNFR binding suggests that some of the identified residues from contacts similar to those found in the TNF-beta/TNFR while others are unique to the CD40-gp39 interaction.

Amino Acid Sequence↗
PubMed1995

Structural basis for pleckstrin homology domain mutations in X-linked agammaglobulinemia.

Deficiencies in a tyrosine kinase, designated Btk, cause X-linked agammaglobulinemia (XLA) in man, a hereditary defect of B-cell differentiation. Mutations in the newly found PH domain located at the N-terminus of Btk have been shown to be the direct cause of XLA, and here two new mutations, T33P and V64F, are presented. Btk is thus far the only protein in which mutations of the PH domain have been found to cause a disease. The three-dimensional structure of the Btk PH domain was modeled on the basis of the dynamin PH structure. Despite a relatively low sequence similarity the Btk PH domain seems to have the same two beta-sheet structure observed in the known structures. The model was used to interpret the structural basis for disease in five independent point mutations and in an insertion in patients with XLA. The mutated residues F25, V64, and V113, and possibly residue(s) around Q103, could form a binding site, since these amino acids are located close to each other on the surface of the molecule.

Agammaglobulinemia↗
PubMed1995

Suppression of human immunoglobulin E antibody production by a new naphthalene derivative.

A new naphthalene derivative, (E)-2-(7-(2-naphthyl)-6-heptenamide)benzoic acid (TEI-8364) was assessed for its effect on interleukin (IL)-4- and anti-CD40 monoclonal antibody-induced immunoglobulin E (IgE) production by cultured human lymphocytes. TEI-8364 preferentially suppressed the production of IgE by peripheral blood mononuclear cells (PBMC) in a dose-dependent manner, without inhibiting PBMC proliferation. In addition, TEI-8364, at a concentration of 10 microM, completely inhibited IL-4- and anti-CD40-induced IgE production by purified tonsillar B lymphocytes, suggesting that TEI-8364 affects B cells by interfering with signals provided by IL-4 or through CD40 and IL-4. TEI-8364 also had a profound inhibiting effect on the in vitro production of specific antibody to a T cell-dependent antigen by PBMC from an immunized volunteer, cultured in the presence of antigen. Furthermore, TEI-8364 at a dose of 1 mg/mouse/day selectively inhibited IgE production by severe combined immunodeficiency mice engrafted with human PBMC, if the drug was administered subcutaneously for five consecutive days. These findings suggest that TEI-8364 is a potent therapeutic agent that may be useful in the treatment of IgE-mediated allergic disorders.

Adult↗