Ayse Metin

Dominant-negative mutations in the DNA-binding domain of STAT3 cause hyper-IgE syndrome

Hyper-immunoglobulin E syndrome (HIES) is a compound primary immunodeficiency characterized by a highly elevated serum IgE, recurrent staphylococcal skin abscesses and cyst-forming pneumonia, with disproportionately milder inflammatory responses, referred to as cold abscesses, and skeletal abnormalities. Although some cases of familial HIES with autosomal dominant or recessive inheritance have been reported, most cases of HIES are sporadic, and their pathogenesis has remained mysterious for a long time. Here we show that dominant-negative mutations in the human signal transducer and activator of transcription 3 (STAT3) gene result in the classical multisystem HIES. We found that eight out of fifteen unrelated non-familial HIES patients had heterozygous STAT3 mutations, but their parents and siblings did not have the mutant STAT3 alleles, suggesting that these were de novo mutations. Five different mutations were found, all of which were located in the STAT3 DNA-binding domain. The patients’ peripheral blood cells showed defective responses to cytokines, including interleukin (IL)-6 and IL-10, and the DNA-binding ability of STAT3 in these cells was greatly diminished. All five mutants were non-functional by themselves and showed dominant-negative effects when co-expressed with wild-type STAT3. These results highlight the multiple roles played by STAT3 in humans, and underline the critical involvement of multiple cytokine pathways in the pathogenesis of HIES.

WASP regulates suppressor activity of human and murine CD4(+)CD25(+)FOXP3(+) natural regulatory T cells.

A large proportion of Wiskott-Aldrich syndrome (WAS) patients develop autoimmunity and allergy. CD4+CD25+FOXP3+ natural regulatory T (nTreg) cells play a key role in peripheral tolerance to prevent immune responses to self-antigens and allergens. Therefore, we investigated the effect of WAS protein (WASP) deficiency on the distribution and suppressor function of nTreg cells. In WAS−/− mice, the steady-state distribution and phenotype of nTreg cells in the thymus and spleen were normal. However, WAS−/− nTreg cells engrafted poorly in immunized mice, indicating perturbed homeostasis. Moreover, WAS−/− nTreg cells failed to proliferate and to produce transforming growth factor β upon T cell receptor (TCR)/CD28 triggering. WASP-dependent F-actin polarization to the site of TCR triggering might not be involved in WAS−/− nTreg cell defects because this process was also inefficient in wild-type (WT) nTreg cells. Compared with WT nTreg cells, WAS−/− nTreg cells showed reduced in vitro suppressor activity on both WT and WAS−/− effector T cells. Similarly, peripheral nTreg cells were present at normal levels in WAS patients but failed to suppress proliferation of autologous and allogeneic CD4+ effector T cells in vitro. Thus, WASP appears to play an important role in the activation and suppressor function of nTreg cells, and a dysfunction or incorrect localization of nTreg cells may contribute to the development of autoimmunity in WAS patients.

Human PMS2 deficiency is associated with impaired immunoglobulin class switch recombination

Immunoglobulin (Ig) class switch recombination (CSR) deficiencies are rare primary immunodeficiencies characterized by the lack of switched isotype (IgG/IgA/IgE) production. In some cases, CSR deficiencies can be associated with abnormal somatic hypermutation. Analysis of CSR deficiencies has helped reveal the key functions of CSR-triggering molecules, i.e., CD40L, CD40, and effector molecules such as activation-induced cytidine deaminase and uracil N-glycosylase. We report a new form of B cell–intrinsic CSR deficiency found in three patients with deleterious, homozygous mutations in the gene encoding the PMS2 component of the mismatch repair machinery. CSR was found partially defective in vivo and markedly impaired in vitro. It is characterized by the defective occurrence of double-strand DNA breaks (DSBs) in switch regions and abnormal formation of switch junctions. This observation strongly suggests a role for PMS2 in CSR-induced DSB generation.

Griscelli Disease: Genotype–Phenotype Correlation in an Array of Clinical Heterogeneity

Griscelli disease is a rare autosomal recessive disorder characterized by diffuse pigmentary dilution and occurrence of acute phases of uncontrolled lymphocyte and macrophage activation, so-called “hemophagocytic syndrome” (HS) that leads to death. Recently, two closely linked genes located on human 15q21 region have been found to be responsible for the disease. We present clinical and laboratory findings of 13 unrelated patients with Griscelli disease as well as mutation analyses in an effort to define a genotype–phenotype correlation. Eight patients who showed RAB27A mutations presented with HS. In contrast, two patients who primarily presented with a neurological impairment in the absence of infection susceptibility or HS were found to have homozygous MYO5A mutations. No mutation in RAB27A could be detected in the other three patients. One of the latter developed HS at a rather late age, while the other two are free of HS at 12 and 15 years of age. Griscelli disease presents with a heterogeneous clinical picture that seems to reflect the involved gene defect. This genotype–phenotype correlation suggests that the natural course of the disease and outcome is dictated by the site and type of the genetic mutation.

Inherited and acquired immunodeficiencies underlying tuberculosis in childhood.

Tuberculosis (TB), caused by Mycobacterium tuberculosis (M.tb) and a few related mycobacteria, is a devastating disease, killing more than a million individuals per year worldwide. However, its pathogenesis remains largely elusive, as only a small proportion of infected individuals develop clinical disease either during primary infection or during reactivation from latency or secondary infection. Subacute, hematogenous, and extrapulmonary disease tends to be more frequent in infants, children, and teenagers than in adults. Life‐threatening primary TB of childhood can result from known acquired or inherited immunodeficiencies, although the vast majority of cases remain unexplained. We review here the conditions conferring a predisposition to childhood clinical diseases caused by mycobacteria, including not only M.tb but also weakly virulent mycobacteria, such as BCG vaccines and environmental mycobacteria. Infections with weakly virulent mycobacteria are much rarer than TB, but the inherited and acquired immunodeficiencies underlying these infections are much better known. Their study has also provided genetic and immunological insights into childhood TB, as illustrated by the discovery of single‐gene inborn errors of IFN‐γ immunity underlying severe cases of TB. Novel findings are expected from ongoing and future human genetic studies of childhood TB in countries that combine a high proportion of consanguineous marriages, a high incidence of TB, and an excellent clinical care, such as Iran, Morocco, and Turkey.

Clinical, functional, and genetic characterization of chronic granulomatous disease in 89 Turkish patients

BACKGROUND Chronic granulomatous disease (CGD) is a rare primary immunodeficiency disorder of phagocytes resulting in impaired killing of bacteria and fungi. A mutation in one of the 4 genes encoding the components p22(phox), p47(phox), p67(phox), and p40(phox) of the leukocyte nicotinamide dinucleotide phosphate reduced (NADPH) oxidase leads to autosomal recessive (AR) CGD. A mutation in the CYBB gene encoding gp91(phox) leads to X-linked recessive CGD. OBJECTIVE The aim of this study is to show the correlation between clinical, functional, and genetic data of patients with CGD from Turkey. METHODS We report here the results of 89 patients with CGD from 73 Turkish families in a multicenter study. RESULTS Most of the families (55%) have an AR genotype, and 38% have an X-linked genotype; patients from 5 families with a suspected AR genotype (7%) were not fully characterized. We compared patients with CGD according to the severity of NADPH oxidase deficiency of neutrophils. Patients with A22(0), A67(0) or X91(0) phenotypes with a stimulation index of 1.5 or less have early clinical presentation and younger age at diagnosis (mean, 3.2 years). However, in p47(phox)-deficient cases and in 5 other AR cases with high residual oxidase activity (stimulation index ≥ 3), later and less severe clinical presentation and older age at diagnosis (mean, 7.1 years) were found. Pulmonary involvement was the most common clinical feature, followed by lymphadenitis and abscesses. CONCLUSION Later and less severe clinical presentation and older age at diagnosis are related to the residual NADPH oxidase activity of neutrophils and not to the mode of inheritance. CGD caused by A22(0) and A67(0) subtypes manifests as severe as the X91(0) subtype.

Impaired IgG Antibody Production to Pneumococcal Polysaccharides in Patients with Ataxia–Telangiectasia

Various factors seem to be etiologic in the susceptibility to sinopulmonary infections in ataxia–telangiectasia (A-T) patients, i.e., low serum and salivary IgA, low serum IgG2, and even aspiration of saliva. S. pneumoniae is a common pathogen responsible from pulmonary infections and impaired antibody response to polysaccharide antigens is seen in patients with IgG2 and IgA deficiency as well as patients with CVID and WAS. We studied IgG-type antibody production to six pneumococcal serotypes in 29 A-T patients by ELISA before and 3–4 weeks after pneumococcal vaccine. The response was considered positive when the antibody titer was >10 U/ml but weak when the titer was 10–20 U/ml. Twenty-two of 29 (76%) patients did not respond to any of the serotypes, 5 (17%) showed a positive response to one serotype, 1 (3.4%) to two serotypes, and 1 (3.4%) to four serotypes. With conversion to gravimetric units (ng IgG/ml) and >1800 ng/ml (300 ng Ab N/ml) considered a positive response, 5 of 29 (17.2%) patients showed a positive response (300 ng ab N/ml) to two or fewer serotypes. All patients tested produced IgG antibody to tetanus toxoid. Sixteen of 27 (59.3%) patients had low IgG2 and four (14.8%) had low IgG3 levels, while 18 (62.1%) of 29 patients had low serum IgA. No correlation was found either between serum Ig isotype levels and antipolysaccharide antibody response or between susceptibility to infection and antibody production. The mechanism responsible for disturbed antipolysaccharide (TI-2 antigen) antibody production in patients with A-T needs to be investigated. It may provide additional information on the function of the ATM gene product and be helpful in clarifying the role of B cells and contribution of T cells in TI-2 responses

Successful bone marrow transplantation for DOCK8 deficient hyper IgE syndrome

Dear Editor, We report a girl with AR-DOCK8 deficiency treated successfully with allogeneic bone marrow transplantation (BMT). She was born to consanguineous parents (cousins) originating from and living in eastern Turkey. The first two children of the family were not diagnosed as immunodeficient despite hypereosinophilia and high IgE levels. They had neonatal onset pruritic eczematous dermatitis, food allergies, recurrent and severe pneumonias (LRTI) when they died at five and six yr old, respectively. Sibling 6 (the propositus) who was born after three healthy children, presented with severe neurological disease: beginning nearly 6–8 months ago with mild ataxia and gradual deterioration with restlessness, spasticity, progressive hearing, speech and vision loss, hyperactive deep tendon reflexes, Babinsky and clonus. Radiological diagnosis of progressive multifocal leukoencephalopathy (PML) with serial MRI was supported by high JCV-DNA in serum and cerebrospinal fluid (2200 copies/mL). He also was diagnosed with hyper IgE syndrome (HIES) caused by the dermatitis of neonatal onset, severe food allergies, LRTIs and high peripheral blood eosinophilia and serum IgE. There were no pneumatoceles despite recurrent pulmonary infections and cold abscesses nor joint hypermobility. We treated him with i.v. immunoglobulin (IVIG) 400 mg/kg/day for 15 days with no clinical response. As the response to rh-interferon-gamma (rhIFN-c) stimulation is shown in Tyk-2 deficient patient (1), we gave rhIFN-c to this patient with PML using 50 lg/m, ·3/wk, by sc route. He died at the age of seven yr with sepsis in our intensive care unit. The last child (DOB: 25 October 2006) of this family also presented with neonatal rash. She developed severe eczema with lichenification since the first months of life. She had multiple food, environmental and drug allergies, including lentil anaphylaxis. At the age of 18 months, she underwent further investigations after the diagnosis of her brother s JCV infection. She presented with severe disseminated ichthyosiform eczema, ectropion of the eyelids, recurrent LRTI, oral, cutaneous and ungual candidiasis. Fortunately, her brain CT was normal and the serum and CSF did not reveal JCV infection as her brother. High levels of IgE (>10 000 IU/mL) and hypereosinophilia (>5000/lL) were persistent. Serum immunoglobulin levels (G: 1580, M: 71 and A: 8.7 mg/dL) were normal except for low IgA for age while lymphocyte phenotyping revealed CD4+ T cell lymphopenia (absolute: 250/lL) with CD3+ T cell 28%, CD19+B cell 60%, CD16+56+ NK cell 5% in the peripheral blood. Her serum anti-HBs, antipolio, anti-HSV, anti-CMV, anti-EBV, anti-IgM and anti-IgG antibodies and isohemagglutinins were absent. The girl was also clinically diagnosed as autosomal recessive-HIES and treatment was initiated with IVIG, itraconazole, sulfamethoxazoletrimethoprim and rhIFN-c for prophylaxis and immune modulation. She was not responding to topical steroids, emollients and oral antihistamines. Genomic DNA of the patient, parents and her brother who died with JCV infection were evaluated for the DOCK8 gene as the possible cause for the phenotype at the Department of Immunology and Molecular Pathology of Royal Free Hospital (London, UK). Engelhardt et al. identified a homozygous large deletion up to and including exon 25 of the DOCK8 gene (c.?_3121?del), deleting the first half of the gene (JACI 2009;124:1289, patients with codes of ARH016.6, ARH016.7) (2). It could not be understood where the exact beginning of the deletion was; the first deleted exon they detected was exon 3, but as they did not analyze exon 1 and 2, it was concluded that the deletion began before or at the start of the DOCK8 gene. Because of recurrent sibling deaths, she was considered for hematopoietic stem cell Pediatr Transplantation 2012: 16: 398–399 2012 John Wiley & Sons A/S.

IL-12Rβ1 deficiency: mutation update and description of the IL12RB1 variation database

IL‐12Rβ1 deficiency is an autosomal recessive disorder characterized by predisposition to recurrent and/or severe infections caused by otherwise poorly pathogenic mycobacteria and salmonella. IL‐12Rβ1 is a receptor chain of both the IL‐12 and the IL‐23 receptor and deficiency of IL‐12Rβ1 thus abolishes both IL‐12 and IL‐23 signaling. IL‐12Rβ1 deficiency is caused by bi‐allelic mutations in the IL12RB1 gene. Mutations resulting in premature stop codons, such as nonsense, frame shift, and splice site mutations, represent the majority of IL‐12Rβ1 deficiency causing mutations (66%; 46/70). Also every other morbid mutation completely inactivates the IL‐12Rβ1 protein. In addition to disease‐causing mutations, rare and common variations with unknown functional effect have been reported in IL12RB1. All these variants have been deposited in the online IL12RB1 variation database (www.LOVD.nl/IL12RB1). In this article, we review the function of IL‐12Rβ1 and molecular genetics of human IL12RB1.

An allelic variant of Griscelli disease: presentation with severe hypotonia, mental-motor retardation, and hypopigmentation consistent with Elejalde syndrome (neuroectodermal melanolysosomal disorder).

Sirs: Griscelli disease, first described in 1978, is a rare autosomal recessive disorder characterized by pigmentary dilution, variable cellular and humoral immunodeficiency, acute phases of lymphocyte and macrophage activation that can lead to pancytopenia, increased serum triglyceride levels, and hypofibrinogenemia [4, 8, 10, 11]. Although neurological involvement was not reported initially, later it was observed that various central nervous system manifestations including hyperreflexia, convulsions, lethargy, coma, regression of developmental milestones, hypertonia, nystagmus, strabismus, and ataxia due to cellular infiltration can develop during the accelerated phase [1, 5, 6, 8, 11]. In 1997 the locus for Griscelli disease was mapped to chromosome 15q21, and two homozygous mutations were found in the Myosin-Va gene that maps to the same region [9]. On the other hand, there is another rare group of patients with hypopigLETTER TO THE EDITORS