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Biomedical subjects

I Tezcan

Publications and source records attributed to I Tezcan.

At least 19 recordsLinked to original sources
PubMed2006

Skewing of X-chromosome inactivation in three generations of carriers with X-linked chronic granulomatous disease within one family.

BACKGROUND: Chronic granulomatous disease (CGD) is an inherited disorder of the innate immune system characterized by impairment of intracellular microbicidal activity of phagocytes. Mutations in one of the four known NADPH-oxidase components preclude generation of superoxide and related antimicrobial oxidants, leading to the phenotype of CGD. Defects in gp91-phox, encoded by CYBB, lead to X-linked CGD, responsible for approximately 70% of all CGD cases. The aim of the study was to evaluate the hypothesis that age-related skewing of X-chromosome inactivation, as described in several CGD families, is caused by preferential survival of bone marrow clones with an inactive NADPH oxidase. MATERIALS AND METHODS: We studied the neutrophils from three patients and four carriers in three generations of a Turkish family with X-linked CGD. Carrier detection was carried out by the dihydrorhodamine (DHR)-1,2,3 assay, which measures on a per-cell basis the NADPH oxidase-dependent oxidation of DHR by phagocytes. The X-chromosome inactivation pattern was determined with the HUMARA assay in DNA from leucocytes as well as in DNA from a buccal smear of the four carriers. RESULTS: The three patients were identified by a negative DHR test, and the mutation in their CYBB gene was characterized by DNA sequencing. Moreover, we found an age-related degree of skewing of X-chromosome inactivation in the leucocytes of the four X-CGD carriers, both at the protein level (NADPH oxidase activity) and at the DNA level (HUMARA assay). However, similar skewing of X-chromosome inactivation was found in the buccal DNA from these women. CONCLUSIONS: These novel findings indicate that the age-related degree of skewing was probably a chance finding, not related to preferential survival of NADPH oxidase-deficient precursor cells, because this enzyme is not expressed in (buccal) epithelial cells.

Adult↗
PubMed2005

Life-threatening neurological complications after bone marrow transplantation in children.

Neurological complications may occur in BMT recipients (11-59%), frequently contributing to morbidity or mortality. They are the main causes of death in 10-15%. Life-threatening neurological complications were seen in 11 out of 113 (9.7%) children who underwent BMT from HLA-matched family (n=7) or mismatched donors (n=4) at our institution. Diagnoses of patients with neurological complications were acute myeloblastic leukemia (AML) (five), thalassemia major (two), Fanconi anemia (two), Omenn syndrome (one) and leukodystrophy (one), and the neurological events were seen between days +13 and +85 after transplantation. Minor symptoms including reversible, nonrepetitive seizures were excluded. Cyclosporine A toxicity was diagnosed in six children. The rest of the complications were brain abscess/meningoencephalitis (two), severe hypomagnesemia (one), busulfan toxicity (one), sustained hypertension (three), and intracranial hemorrhage (three). Six patients with neurological complications suffered from >grade II graft-versus-host disease (GvHD), and all were high risk for transplant-related complications. In this study, risk status of the underlying disease, mismatched transplantation, a diagnosis of AML (advanced stage), older age and >grade II GvHD were important adverse factors for the development of severe life-threatening neurological complications.

Adolescent↗
PubMed2003

Serum zinc and alkaline phosphatase values in pediatric bone marrow transplantation patients.

Zinc (Zn) plays an important role in the maintenance of immune functions, including cellular/humoral immunity, and in the prevention of oxidative injury. Therefore, the maintenance of a normal Zn status may be important in bone marrow transplantation (BMT) patients. Serum Zn levels were determined in 35 children during the BMT period. In addition, as Zn-related factors, serum Cu levels and alkaline phosphatase (AP) activity were also measured. There was a significant decrease in Zn and AP values during the immediate post-transplant period (lowest at day +7) when compared to pre-BMT levels (p <.01). The patients who developed hypozincemia were more likely to be transplanted for a diagnosis of malignant disorder and were younger, and adverse events appeared to occur more frequently. This preliminary study suggests that maintaining a normal Zn status may be important in BMT patients and that Zn deficiency may be a risk factor for adverse events.

Adolescent↗
PubMed2001

The mutational spectrum of human malignant autosomal recessive osteopetrosis.

Human malignant infantile osteopetrosis (arOP; MIM 259700) is a genetically heterogeneous autosomal recessive disorder of bone metabolism, which, if untreated, has a fatal outcome. Our group, as well as others, have recently identified mutations in the ATP6i (TCIRG1) gene, encoding the a3 subunit of the vacuolar proton pump, which mediates the acidification of the bone/osteoclast interface, are responsible for a subset of this condition. By sequencing the ATP6i gene in arOP patients from 44 unrelated families with a worldwide distribution we have now established that ATP6i mutations are responsible for approximately 50% of patients affected by this disease. The vast majority of these mutations (40 out of 42 alleles, including seven deletions, two insertions, 10 nonsense substitutions and 21 mutations in splice sites) are predicted to cause severe abnormalities in the protein product and are likely to represent null alleles. In addition, we have also analysed nine unrelated arOP patients from Costa Rica, where this disease is apparently much more frequent than elsewhere. All nine Costa Rican patients bore either or both of two missense mutations (G405R and R444L) in amino acid residues which are evolutionarily conserved from yeast to humans. The identification of ATP6i gene mutations in two families allowed us for the first time to perform prenatal diagnosis: both fetuses were predicted not to be affected and two healthy babies were born. This study contributes to the determination of genetic heterogeneity of arOP and allows further delineation of the other genetic defects causing this severe condition.

Amino Acid Sequence↗
PubMed2001

Artemis, a novel DNA double-strand break repair/V(D)J recombination protein, is mutated in human severe combined immune deficiency.

The V(D)J recombination process insures the somatic diversification of immunoglobulin and antigen T cell receptor encoding genes. This reaction is initiated by a DNA double-strand break (dsb), which is resolved by the ubiquitously expressed DNA repair machinery. Human T-B-severe combined immunodeficiency associated with increased cellular radiosensitivity (RS-SCID) is characterized by a defect in the V(D)J recombination leading to an early arrest of both B and T cell maturation. We previously mapped the disease-related locus to the short arm of chromosome 10. We herein describe the cloning of the gene encoding a novel protein involved in V(D)J recombination/DNA repair, Artemis, whose mutations cause human RS-SCID. Protein sequence analysis strongly suggests that Artemis belongs to the metallo-beta-lactamase superfamily.

Amino Acid Sequence↗
PubMed2001

High levels of delayed radiation-induced apoptosis observed in lymphoblastoid cell lines from ataxia-telangiectasia patients.

PURPOSE: Cells from ataxia-telangiectasia (A-T) patients are extremely sensitive to radiation but display decreased apoptosis, as measured during the first 3 days following radiation. To explain this apparent contradiction, we examined apoptosis in normal and A-T cells at late time points following radiation, under the assumption that radiation-induced apoptosis is delayed in the A-T cells. METHODS AND MATERIALS: Blood cells and lymphoblastoid cell lines from A-T patients, as well as healthy donors, were irradiated with X-rays. Apoptosis was measured at different time points (up to 7 and 30 days for lymphocytes and lymphoblastoid cells, respectively) using a flow cytometric method based on the reduction of intracellular DNA content (sub-G1 population). RESULTS: Compared to normal cells, CD4 and CD8 A-T lymphocytes displayed constantly reduced levels of radiation-induced apoptosis for up to 7 days after treatment. A-T lymphoblastoid cells, however, displayed a delayed and prolonged apoptosis. CONCLUSION: A-T lymphoblastoid cells show high levels of delayed radiation-induced apoptosis, which may contribute to the high cellular radiosensitivity displayed by the A-T phenotype. ATM (the gene mutated in A-T) plays different roles in the apoptotic response to ionizing radiation in quiescent lymphocytes and proliferative lymphoblastoid cells.

Adolescent↗
PubMed2001

Bruton tyrosine kinase gene mutations in Turkish patients with presumed X-linked agammaglobulinemia.

X-linked agammglobulinemia (XLA) is a ptototypical humoral immunodeficiency caused by mutations in the gene coding for Bruton tyrosine kinase (BTK). The genetic defect in XLA impairs early B cell development resulting in marked reduction of mature B cells in the blood. Studies from different countries have demonstrated that approximately 90% of males with presumed XLA bear mutations in BTK. In this study, we report for the first time the occurrence of BTK mutations in Turkey. We performed mutational analysis of the BTK gene in 16 Turkish male patients from 13 separate families with presumed XLA based on abnormally low peripheral blood B-cell numbers (lt; 1%), hypogammaglobulinemia, and recurrent bacterial infections. We found that in nine of the 13 families (69%) a Btk mutation caused XLA. Two of the mutations were previously described, but seven novel mutations were identified: two missense (Y39C, G584R), one nonsense (Q343X), and 4 deletions (1800-1821del, 1843-1847del, 1288-1292del, 291del) resulting in frameshift and premature stop codon. By contrast, no mutations in the BTK gene were identified in the other 4 families. A consanguinity in three of these families raises the possibility that mutations in other autosomal genes which affect early B cell development may contribute to their phenotype resembling XLA.

Adolescent↗
PubMed2001

Pneumatosis intestinalis in an infant undergoing bone marrow transplantation for Wiskott-Aldrich syndrome.

A 7-month-old patient with Wiskott-Aldrich syndrome (WAS) developed pneumatosis intestinalis (PI) in the immediate post-transplant period after receiving paternal human leucocyte antigen (HLA) phenotypically matched bone marrow (BM). PI has been described in patients with congenital or acquired immunodeficiency states and after bone marrow transplantation (BMT). To our knowledge, the condition has not been described in WAS. The underlying bowel mucosa damage as a result of the history of massive rectal bleeding, the effects of the conditioning regimen, immunosuppression, neutropenia, and infection, may all have contributed to the development of PI. Although the condition resolved by conservative management alone, the patient developed Klebsiella pneumonia sepsis, interstitial pneumonitis, failed to engraft, and died on day +66 following a second infusion of stem cells mobilized from his father's peripheral blood.

Bone Marrow Transplantation↗
PubMed2001

The analysis of eosinophil and lymphocyte phenotype following single dose of high-dose methylprednisolone in two siblings with marked hypereosinophilia.

The effect of single high-dose methylprednisolone (HDMP) on eosinophil and lymphocyte phenotype in two siblings with marked hypereosinophilia was investigated. Since conventional dose steroids failed to produce a haematological and clinical response in case one, both children were given HDMP (20 mg/kg/day). Eosinophils and lymphocytes showed an activated state before treatment, characterized by marked expression of CD11b, CD18, CD45RO on eosinophils and increased HLA-DR, CD95, CD18, CD38 on lymphocytes. Twenty-four hours after administration of HDMP a dramatic reduction in peripheral blood eosinophil count was observed in both patients associated with phenotypic changes characterized by decreased expression of CD11b, CD18, CD13 and increased CD95 expression in one. Furthermore, HDMP treatment induced a drop in the expression of CD95 and CD18 on lymphocytes. These changes may suggest a suppressive role for HDMP on eosinophil and lymphocyte activation which may have contributed to the haematological and clinical response.

Antigens, CD↗
PubMed2001

Evaluation of coagulation in pediatric bone marrow transplantation patients.

A hypercoagulable state is frequently described in adult patients undergoing bone marrow transplantation (BMT). In this study, the coagulation profile of 29 children was prospectively investigated in the pre- and post-transplant period. A significant rise in the activated partial thromboplastin time (aPTT) values was detected on days 7 and 14 after transplantation. Moreover, an increase in the d-dimer level was also notable, regardless of the clinical condition of the patients. The other coagulation parameters investigated (i.e. protein S, protein C, anti-thrombin III, factor VIII, von Willebrand factor, and prothrombin time) remained essentially unchanged. However, hyper-fibrinogenemia was observed in all patients with chronic myeloid leukemia (CML) (n=5) before and after transplantation. In summary, in the present study pediatric bone marrow transplantation patients did not show a hyper-coagulable state after marrow infusion. However, a significant rise in PTT and d-dimer values were noted.

Adolescent↗
PubMed2000

Activation-induced cytidine deaminase (AID) deficiency causes the autosomal recessive form of the Hyper-IgM syndrome (HIGM2).

The activation-induced cytidine deaminase (AID) gene, specifically expressed in germinal center B cells in mice, is a member of the cytidine deaminase family. We herein report mutations in the human counterpart of AID in patients with the autosomal recessive form of hyper-IgM syndrome (HIGM2). Three major abnormalities characterize AID deficiency: (1) the absence of immunoglobulin class switch recombination, (2) the lack of immunoglobulin somatic hypermutations, and (3) lymph node hyperplasia caused by the presence of giant germinal centers. The phenotype observed in HIGM2 patients (and in AID-/- mice) demonstrates the absolute requirement for AID in several crucial steps of B cell terminal differentiation necessary for efficient antibody responses.

APOBEC-1 Deaminase↗
PubMed2000

Two genes are responsible for Griscelli syndrome at the same 15q21 locus.

Griscelli syndrome is a rare autosomal recessive disease characterized by pigment dilution, variable cellular immunodeficiency, and an acute phase of uncontrolled T lymphocyte and macrophage activation. We previously mapped the disease locus to 15q21 and showed that a MyoVa gene (HGMW-approved symbol MYO5A) defect leads to Griscelli syndrome. We report a second MyoVa mutation in a new patient, confirming this first finding. However, in four other Griscelli syndrome patients analyzed, the MYOVA protein is expressed, and no mutation can be detected in the MyoVa gene coding sequence, even in the alternatively spliced region for which exon-intron boundaries were characterized. Linkage analysis performed in 15 Griscelli families thus far studied confirms the first localization. However, fine haplotype analysis in three families strongly suggests the existence of a second gene at the same locus for Griscelli syndrome less than 7.3 cM distant from the MyoVa gene.

Alternative Splicing↗
PubMed2000

T-ALL with monoclonal gammopathy and hairy cell features.

The presented case is a boy with T-cell acute lymphoblastic leukemia (ALL) with hairy cell (HC) features and monoclonal gammopathy. The disease process had an acute onset and followed a rapid, progressive course. The patient had minimal splenomegaly and bicytopenia, but the bone marrow displayed increased numbers of reticulin fibers. The blasts were positive for tartrate-resistant acid phosphatase (TRAP) and CD11c. Molecular analysis revealed rearrangement of immunoglobulin heavy chain genes and a rearranged T-cell receptor (TcRbeta) beta gene. The patient responded to conventional ALL therapy. Acute T-cell ALL with HC features in childhood has not been reported previously, either alone or in association with monoclonal gammopathy. We propose "T-ALL with hairy cell features" to describe this case.

Adolescent↗
PubMed2000

Isolated cutaneous response to granulocyte-monocyte colony stimulating factor in fatal idiopathic disseminated Bacillus-Calmette-Guerin infection.

UNLABELLED: Severe disseminated Bacillus-Calmette-Guerin (BCG) infection is very rare and has been regarded as idiopathic when no immunodeficiency is present. This entity seems to be due to several new types of inherited abnormalities in the pathways important in defence against Mycobacteria. Although improvement with interferon-gamma (IFN-gamma) has been reported in some patients, to our knowledge there are no reports on the effect of other cytokines in the treatment of these patients. We report here the clinical response to IFN-gamma and granulocyte-monocyte colony stimulating factor (GM-CSF) treatment in a patient with idiopathic disseminated BCG infection who failed to respond to multiple antimycobacterial agents. The patient showed partial and transitory response to IFN-gamma, however, GM-CSF treatment led to rapid improvement of skin lesions within 2 weeks without any effect on the progression of the disease in the other organ systems. CONCLUSION: The response of idiopathic disseminated Bacillus-Calmette-Guerin infection to granulocyte-monocyte colony stimulating factor treatment was limited to cutaneous lesions. Granulocyte-monocyte colony stimulating factor may have acted to promote wound healing or the levels of this factor achieved in other affected organs may have been inadequate.

BCG Vaccine↗
PubMed2000

Transient hypogammaglobulinemia of infancy: clinical and immunologic features of 40 new cases.

BACKGROUND: Transient hypogammaglobulinemia of infancy (THI) results from a delay in the maturation of immunoglobulin production. METHODS: The clinical and immunologic data of 40 patients with THI are presented. Clinically, the majority of patients presented with recurrent respiratory infections and otitis media, bronchitis and/or bronchial asthma and recurrent gastroenteritis. RESULTS: Ten of 40 children had isolated low IgG; isolated low IgA and isolated low IgM were detected in one and three patients, respectively. At initial evaluation, levels of all three immunoglobluins were low in nine patients. Ten patients had diminished IgG and IgA levels, six had diminished IgA and IgM levels and one had low IgG and IgM levels. Two patients were given intravenous immunoglobulin replacement therapy for 1 year. None of the patients has experienced serious infections during their follow-up period. CONCLUSIONS: Prospective evaluation of patients (age range 5-60 months) revealed that immunoglobulin levels in 33 patients recovered before 36 months of age. Seven patients still had low immunoglobluin levels at 40-57 months of age. Three of these patients had low levels of both IgG and IgA, while two patients had low IgM levels and a further two patients had low IgA levels.

Agammaglobulinemia↗
PubMed2000

Polymorphism of the fourth component of complement in Turks.

An analysis of polymorphism in the fourth component of human complement (C4) was performed on EDTA-plasma from 142 unrelated, randomly selected Turks without collagen-vascular disease or recurrent infections. Plasma samples treated with neuraminidase and carboxypeptidase-B were subjected to high-voltage agarose gel electrophoresis followed by immunofixation. C4B allotypes were further detected in some samples by Western blots with monoclonal antibody 1228 (anti-C4B/Ch1 reactivity). The frequencies of C4A and C4B alleles were determined. Allele C4B*5, which has been found to be relatively common in Asian (Oriental) populations, was not detected in this study. No specific predilection could be noted among the rare variants. C4A*3-C4B*1 was the most common haplotype (n = 40/142, or 28%) but was found less frequently than in Caucasian populations. This finding may be the result of the limited number of samples examined. C4A and/or C4B null allotypes were seen in 49 of 142 (34.6%) subjects. The most frequent C4 null allotype seen was C4B null (37/142, or 26%): 28 subjects had one C4B null allele; 1 had a homozygous deficiency of C4B (C4B*QO, *QO) and 7 had C4A*QO C4B*QO, a double heterozygous haplotype. Frequencies of homozygous haplotype C4A*Q0-C4B*Q0 in the population studied were found to be 0.007. The results of this study demonstrate that the genetic composition of the Turkish population exhibits both similarities and differences with the European population, and ranges between Caucasian and Mongoloid (Asian) populations.

Alleles↗
PubMed1999

Incomplete T-cell immune reconstitution in two major histocompatibility complex class II-deficiency/bare lymphocyte syndrome patients after HLA-identical sibling bone marrow transplantation.

To study the effects of major histocompatibility complex (MHC) class II expression on T-cell development, we have investigated T-cell immune reconstitution in two MHC class II-deficiency patients after allogeneic bone marrow transplantation (allo-BMT). Our study showed that the induction of MHC class II antigen expression on BM graft-derived T cells in these allo-BMT recipients was hampered upon T-cell activation. This reduction was most striking in the CD8(+) T-cell subset. Furthermore, the peripheral T-cell receptor (TCR) repertoire in these graft-derived MHC class II-expressing CD4(+) and in the CD8(+) T-cell fractions was found to be restricted on the basis of TCR complementarity determining region 3 (CDR3) size profiles. Interestingly, the T-cell immune response to tetanus toxoid (TT) was found to be comparable to that of the donor. However, when comparing recipient-derived TT-specific T cells with donor-derived T cells, differences were observed in TCR gene segment usage and in the hydropathicity index of the CDR3 regions. Together, these results reveal the impact of an environment lacking endogenous MHC class II on the development of the T-cell immune repertoire after allo-BMT.

Bone Marrow Transplantation↗