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H B Gaspar

Publications and source records attributed to H B Gaspar.

29 records · Page 2Linked to original sources
PubMed2000

Kinase mutant Btk results in atypical X-linked agammaglobulinaemia phenotype.

X-linked agammaglobulinaemia (XLA) is a B cell humoral abnormality arising from mutations in the gene encoding Bruton's tyrosine kinase (Btk). The phenotype of XLA can be variable, with some individuals having a less severe immunophenotype, although in most cases this cannot be correlated with the Btk mutation or expression of Btk protein. In this study we describe clinical and immunological heterogeneity within the same pedigree. Analysis of the genetic defect identified a missense mutation in the kinase domain of Btk which, unusually, preserved Btk protein expression but at reduced levels, and also considerably diminished autophosphorylation activity. Structural analysis of the effect of this mutation on the kinase domain suggests that this mutation is not an integral part of the ATP or substrate binding domains but may affect the interaction of the kinase domain with its own kinase domain and other substrates. Together, these data may provide an explanation for the variable XLA phenotype.

Adult↗
PubMed2000

Short limbed skeletal dysplasia associated with combined immunodeficiency and congenital subglottic stenosis: a new constellation of features.

A newborn male is described with an association of short limbed dwarfism with hip dislocation, combined immunodeficiency characterized by absent B cells and CD4 lymphopaenia and congenital subglottic stenosis. This constellation of abnormalities is distinct from other described skeletal dysplasias associated with immunodeficiency such as ADA deficiency and cartilage hair hypoplasia.

CD4 Lymphocyte Count↗
PubMed2000

Immunogenetics: changing the face of immunodeficiency.

Tables 1 and 2 highlight the enormous advances that have been made in the definition of the molecular defects underlying primary immunodeficiencies in the past decade. The identification of SAP as the gene defective in XLP now completes the molecular bases of all the recognised X linked syndromes. Of the autosomally inherited syndromes, only the genes for DiGeorge syndrome, hyper-IgE, and perhaps most importantly, common variable immunodeficiency remain to be elucidated. The major clinical benefits of this information have primarily been in offering more accurate and rapid molecular diagnoses. The ability to make a molecular diagnosis also increases the options for earlier definitive treatments such as bone marrow transplantation and somatic gene therapy. Finally, as illustrated by the studies on the functions of WASP and the gamma c/JAK-3 pathway, identification of the gene defect is the first step to understanding the molecular pathogenesis of the immunological abnormalities.

Agammaglobulinemia↗
PubMed1998

Absence of expression of the Wiskott-Aldrich syndrome protein in peripheral blood cells of Wiskott-Aldrich syndrome patients.

Wiskott-Aldrich syndrome (WAS) is an X-linked primary immunodeficiency that is usually associated with thrombocytopenia and eczema. The very variable phenotype of WAS results from defects in the WAS protein (WASP), the function of which is not well understood. In many cases causative mutations have now been identified in the WAS gene. Attempts have been made to correlate the nature of the mutations with the severity of the disease. In this study we investigated mutations in 13 patients with WAS and analyzed the expression of WASP in patient blood samples by immunoblot analysis. We found that despite extensive variation in the nature of the mutations in patients with severe WAS symptoms, none express the protein. However, in 1 patient with a mild clinical phenotype WASP expression was detected. Such an analysis could be used as an initial screening procedure for the diagnosis of WAS prior to genotypic analysis.

Base Sequence↗
PubMed1998

Bruton's tyrosine kinase expression and activity in X-linked agammaglobulinaemia (XLA): the use of protein analysis as a diagnostic indicator of XLA.

Mutations in the Bruton's tyrosine kinase (BTK) gene result in XLA. Despite the large numbers of BTK mutations reported, no correlation can be made between the clinical phenotype and the gene defects. Analysis of Btk protein expression and activity in individuals with XLA was performed to characterize the relationship between a particular mutation, the resultant Btk protein and the clinical phenotype. In most patients studied, including those with atypical phenotypes, there was complete absence of protein expression and activity. Furthermore, in two undiagnosed individuals with a clinical phenotype suggestive of XLA, lack of protein expression was used to confirm an abnormality in Btk. These results underline the importance of protein analysis prior to speculating on protein structure and function based on the gene mutation. Lack of Btk expression in atypical phenotypes suggests that there is redundancy in B lymphocyte signalling such that alternative signalling molecules, or mechanisms, can compensate for the lack of Btk. We also suggest that analysis of Btk expression can be used as an indicator of XLA. These rapid assays may be used to screen a wider spectrum of individuals with humoral immunodeficiency in order to characterize fully the extent of Btk deficiency.

Agammaglobulinaemia Tyrosine Kinase↗
PubMed1997

Immunodeficiency syndromes and recurrent infection.

Individuals with increased susceptibility to infection may have an acquired or inherited abnormality of the immune system. In the second of two reviews we aim to outline some of the most important immunodeficiency syndromes that may be associated with a clinical presentation of frequent infection. Awareness of such syndromes may aid pattern recognition and the appropriate investigation of patients with recurrent infection.

Disease Susceptibility↗
PubMed1994

Expression of Bruton's tyrosine kinase protein within the B cell lineage.

Defects in the gene encoding Bruton's tyrosine kinase (Btk), normally expressed in B cells, cause X-linked agammaglobulinemia (XLA). The phenotype of XLA is characterized by a lack of circulating B cells and immunoglobulin. It has been suggested that B cell maturation from the pre-B cell stage to more mature stages is dependent on the appropriate expression of this gene. The Btk mRNA is expressed in B cells and myeloid cells, but protein expression in relation to B cell maturation has not been determined. Moreover, expression of the Btk protein has so far only been investigated in human Epstein-Barr virus-transformed B cell lines, and in murine splenocytes and B cell lines. We have developed an antiserum which recognizes the human Btk protein and shown that normal human tonsillar B cells, peripheral blood monocytes and myeloid cells express the protein, whereas tonsil-derived T cells do not. We also show that the protein is present in early and mature human B cell lines, but is absent in terminally differentiated plasma cell lines. Furthermore, expression is reduced or absent in three B lineage cell lines derived from two patients with defined genetic mutations in Btk and suffering from XLA.

Agammaglobulinaemia Tyrosine Kinase↗
PubMedDate not supplied

Investigation of the immune system in recurrent infection.

Individuals with increased susceptibility to infection may have an acquired or inherited abnormality of the immune system. The complexities of human immunity are such that to investigate the cause may appear a daunting prospect. However, in this review we aim to outline the basic components of the immune system and to provide a logical and stepwise approach to the investigation of immunodeficient individuals.

Adolescent↗