Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0021051 (immunodeficiency)
 71,517 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Mutations in the gene encoding the protein tyrosine kinase Btk are associated with the human B cell immunodeficiency X-linked agammaglobulinemia (XLA). In the mouse, a point mutation in the Btk pleckstrin homology domain segregates with a milder X-linked immunodeficiency (xid). To assess the importance of Btk function in murine lymphopoiesis, we generated multiple embryonic stem cell clones bearing a targeted disruption of the btk gene and examined their potential to produce lymphocytes in both C57BL/6 and RAG2-/- host chimeric animals. These mice provide a complementary set of in vivo competition assays that formally establish the genetic basis for the xid phenotype. Although the null mutation yields a phenotype quite similar to that of xid, it also compromises expansion of B cell precursors. Our results suggest that the murine and human consequences of Btk deficiency differ only quantitatively, and represent the same disease process.
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PMID:Impaired expansion of mouse B cell progenitors lacking Btk. 755 95

We tested for infection with hepatitis C virus (HCV) in 58 patients affected by humoral immunodeficiencies: 43 common variable immunodeficiency (CVI), two hyper IgM syndrome (HIM), two IgG subclass deficiency, four ataxia-telangiectasia (AT), and seven X-linked agammaglobulinaemia (XLA). While the assessment of serum specific HCV antibodies in some of these patients was not informative because of the impairment in specific antibody production, the reverse transcriptase polymerase chain reaction (RT-PCR) assay used to detect serum HCV RNA was a useful method for diagnosing infection. We found that 38% of late onset hypogammaglobulinaemic patients (CVI, HIM or IgG subclass deficiency) had evidence of HCV infection. HCV infection was not detectable in patients with XLA or AT. The majority of our patients had persistent viraemia, and those who underwent liver biopsy showed histological findings of chronic hepatitis. Moreover, we could demonstrate in vitro that eight of 18 HCV-infected patients were actively producing anti-HCV antibodies, despite their impaired antibody production. The high rate of HCV infection in hypogammaglobulinaemic patients could be related to several nosocomial routes of transmission, including intravenous immune globulin administration. Despite the persistent viremia only two patients had cirrhosis and none had hepatocarcinoma.
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PMID:HCV infection in patients with primary defects of immunoglobulin production. 755 76

Investigation of common variable immunodeficiency (CVI) is hampered by lack of a suitable in vitro models. We have developed EBV-transformed B lymphoblastoid cell lines from a selected subset of CVI patients and characterized them for phenotypic and functional properties that provide evidence for their representation of the CVI disease state. B cell lines from the patients expressed increased levels of sIgM and reduced levels of sIgD and sIgG. Essentially none of the CVI-derived B cell lines produced IgG and IgA while all produced IgM, in contrast to normal B cell lines that produced large amounts of IgG and IgM and detectable levels of IgA. Expression of CD95 (fas/Apo-1), a molecule that can induce apoptosis, was increased on the CVI B cell lines while CD38, a novel signaling molecule whose stimulation may prevent apoptosis, showed reduced expression. The B cell lines from the CVI patients exhibit increased apoptosis in vitro spontaneously, in response to anti-CD95 mAb and to X-irradiation. These phenotypic and functional changes are similar to findings on freshly derived B cells from the patients. EBV-derived B cell lines from patients with hyper-IgM immunodeficiency and X-linked agammaglobulinemia did not demonstrate increased CD95 expression or enhanced apoptosis. Thus the EBV-derived B cell lines from our selected CVI patients manifest many characteristics of the patients' fresh cells and may provide critical reagents for the further elucidation of the nature of the B cell dysfunction in the selected subset of CVI patients.
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PMID:B cell lines from a subset of patients with common variable immunodeficiency undergo enhanced apoptosis associated with an increased display of CD95 (Apo-1/fas), diminished CD38 expression, and decreased IgG and IgA production. 758 84

Bruton's tyrosine kinase (Btk) has been identified as the protein responsible for the primary immunodeficiency X-linked agammaglobulinemia (XLA) and has been described as a new member of Src-related cytoplasmic protein tyrosine kinases. We have recently characterized the structure of the entire gene encoding Btk and developed a polymerase chain reaction (PCR)-based assay to detect germline mutations within it. In this report we describe six mutations, five of which are novel, of the Btk gene in patients with XLA and demonstrate the inheritance pattern of the defect within the families of the affected individuals. The mutations found include two nonsense and two missense mutations, a single base deletion at an intron acceptor splice site, and a 16-bp insertion. A single strand conformation polymorphism was also found in the 5' end of intron 8 with the same assay. This technique has provided a powerful tool for direct analysis of the Btk gene for the diagnosis of XLA and carrier detection. The identification of new mutations may eventually reveal the role of Btk in the signaling pathways involved in B-cell development.
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PMID:Characterization of germline mutations of the gene encoding Bruton's tyrosine kinase in families with X-linked agammaglobulinemia. 762 83

X-linked agammaglobulinemia, a B cell immunodeficiency, is caused by mutations in the Bruton's tyrosine kinase (Btk) gene. The absence of a functional Btk protein leads to a failure of B cell differentiation and antibody production. B cell receptor stimulation leads to the phosphorylation of the Btk protein and it is, therefore, likely that Btk is involved in B cell receptor signaling. As a nonreceptor tyrosine kinase, Btk is likely to interact with several proteins within the context of a signal transduction pathway. To understand such interactions, we have generated glutathione S-transferase fusion proteins corresponding to different domains of the human Btk protein. We have identified a 120-kD protein present in human B cells as being bound by the SH3 domain of Btk and which, after B cell receptor stimulation, is one of the major substrates of tyrosine phosphorylation. We have shown that this 120-kD protein is the protein product of c-cbl, a protooncogene, which is known to be phosphorylated in response to T cell receptor stimulation and to interact with several other tyrosine kinases. Association of the SH3 domain of Btk with p120cbl provides evidence for an analogous role for p120cbl in B cell signaling pathways. The p120cbl protein is the first identified ligand of the Btk SH3 domain.
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PMID:The protein product of the c-cbl protooncogene is phosphorylated after B cell receptor stimulation and binds the SH3 domain of Bruton's tyrosine kinase. 762 18

X-linked agammaglobulinaemia (XLA) is an inherited immunodeficiency resulting from mutations in the gene for a cytoplasmic protein tyrosine kinase (Btk). We have utilised reverse-transcription-based PCR in combination with the chemical cleavage and mismatch technique (CCM) to screen for Btk mutations in 42 unrelated patients having classical XLA or 'leaky' XLA-like phenotypes. A variety of mutations, including point mutations, large deletions and splicing defects were detected using this strategy. In total, 20 mutations were found in these patients. All the mutations were different with the exception of three unrelated patients who all showed the same Arg-->His amino acid substitution (R641H) at a highly-conserved residue in the kinase domain. We have also used structural modelling of the Btk kinase domain to predict how two different amino acid substitution mutations at highly-conserved residues are likely to affect the Btk kinase activity.
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PMID:Identification of Btk mutations in 20 unrelated patients with X-linked agammaglobulinaemia (XLA). 763 20

X-linked agammaglobulinemia is a primary inherited immunodeficiency resulting in a lack of or dramatic reduction in the number of mature B lymphocytes and, thus, greatly reduced levels of serum immunoglobulin. The defect results from mutations in the gene for Bruton's tyrosine kinase (Btk). Using rabbit antisera generated against Btk, we have demonstrated an increase in the level of in vitro kinase activity present in anti-Btk immunoprecipitates from B cells following stimulation with anti-immunoglobulin antibody. This increase in immune complex kinase activity is detectable 1 to 2 min following stimulation and remains elevated for over 30 min. A similar increase was not seen with two late pre-B cell lines investigated in the same way. This stimulation of activity may suggest a role for Btk in signalling through the B cell receptor or associated proteins, in mature B cells.
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PMID:The protein defective in X-linked agammaglobulinemia, Bruton's tyrosine kinase, shows increased autophosphorylation activity in vitro when isolated from cells in which the B cell receptor has been cross-linked. 773 82

Carrier detection in X-linked immunodeficiencies (X-SCID, WAS, XLA) relies on the demonstration of non-random X inactivation patterns in blood cell lineages. Only a limited number of cells are available after cell separation methods. PCR-based techniques are therefore necessary to analyze active and inactive X chromosomes. Amplifying a polymorphic CAG repeat in the first exon of the androgen receptor gene after selective digestion of the active X chromosome with a methylation-sensitive restriction enzyme allows to distinguish between the paternal and maternal alleles and to identify their methylation status. DNA from B-, T-lymphocytes and total peripheral leukocytes of normal males, females and obligate carriers of X-linked immunodeficiencies were analyzed. The results of this PCR-based X inactivation assay are concordant with the standard methylation studies at the DXS255 locus using Southern blotting. This PCR assay provides a rapid and informative (heterozygosity > 90%) method in carrier detection of X-linked immunodeficiencies and other X-linked disorders, which show non-random X inactivation in cell lineages from the affected tissues.
Immunodeficiency 1995
PMID:A PCR based X-chromosome inactivation assay for carrier detection in X-linked immunodeficiencies using differential methylation of the androgen receptor gene. 774 38

The defective gene responsible for the recessively inherited immunodeficiency X-linked agammaglobulinemia (XLA) has been shown to encode a cytoplasmic protein tyrosine kinase of the Src family designated Btk (Bruton's tyrosine kinase). To facilitate the search for germline mutations of the Btk gene, we have characterized its genomic structure. Eighteen introns were positioned within the approximately 37 kb gene. Each of the exon/intron boundaries were defined and sequenced, and all but two conform to consensus sequences. We have utilized the genomic organization of Btk and the intervening sequence data to design an assay for amplifying each of the 19 exons from XLA patient DNA for single strand conformation polymorphism (SSCP) analysis. By using this method we have identified mutations in 12 of 14 unrelated affected males: seven different base substitutions and two small deletions. Two of the mutations described in exon 15 of the kinase domain were found in more than one patient and may represent a mutation hot spot. Exon scanning has proven to be a valuable method for identifying the patient mutations in genomic DNA without the use of cDNA. The mutations are easily confirmed with direct sequencing of the amplified exons. This approach will greatly benefit XLA family studies involving carrier detection and prenatal diagnosis. In addition, the mutations identified may reveal residues involved in the specific protein interactions necessary in the B-cell developmental pathway, of which Btk is an integral component.
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PMID:Genomic organization of the Btk gene and exon scanning for mutations in patients with X-linked agammaglobulinemia. 788 Mar 20

Serum immunoreactive interleukin (IL-)1 alpha, IL-4, IL-6 and tumor necrosis factor (TNF) alpha were measured in 42 patients with primary hypogammaglobulinemia (25 common variable immunodeficiency (CVI), 10 congenital hypogammaglobulinemia (CH), 7 X-linked agammaglobulinemia (XLA), and in 21 healthy controls. The cytokine levels were correlated to other immunological parameters including serum levels of neopterin and soluble CD8 (sCD8) antigen. IL-6 was detectable in 48% and IL-4 in 36% of the CVI patients, but in none of the controls. Seventy-five percent of the CVI patients with elevated IL-4 levels had detectable IL-6. In contrast, no patients in the XLA group and only three CH patients had detectable IL-4 or IL-6 levels. TNF alpha and IL-1 alpha were detected in only a few serum samples with no significant differences between patients and controls. In the CVI group elevated IL-6 levels were significantly associated to reduced numbers of CD4+ and CD19+ lymphocytes, elevated levels of neopterin and sCD8 antigen, and occurrence of splenomegaly and bronchiectasis. The raised IL-6 levels were confirmed in longitudinal testing, probably reflecting a characteristic immunological dysregulation in these patients. Cytokine alterations may play a role in the pathogenesis of the immunodeficiency and for the clinical manifestations in CVI patients. Alternatively, elevated cytokine levels may be only a marker of chronic immune activation, particularly in monocytes, possibly delineating a distinct subgroup of patients within the heterogeneous CVI group.
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PMID:Elevated serum levels of interleukin-4 and interleukin-6 in patients with common variable immunodeficiency (CVI) are associated with chronic immune activation and low numbers of CD4+ lymphocytes. 790 14


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