Safa Barış

DOCK8 functions as an adaptor that links TLR-MyD88 signaling to B cell activation

The adaptors DOCK8 and MyD88 have been linked to serological memory. Here we report that DOCK8-deficient patients had impaired antibody responses and considerably fewer CD27+ memory B cells. B cell proliferation and immunoglobulin production driven by Toll-like receptor 9 (TLR9) were considerably lower in DOCK8-deficient B cells, but those driven by the costimulatory molecule CD40 were not. In contrast, TLR9-driven expression of AICDA (which encodes the cytidine deaminase AID), the immunoglobulin receptor CD23 and the costimulatory molecule CD86 and activation of the transcription factor NF-κB, the kinase p38 and the GTPase Rac1 were intact. DOCK8 associated constitutively with MyD88 and the tyrosine kinase Pyk2 in normal B cells. After ligation of TLR9, DOCK8 became tyrosine-phosphorylated by Pyk2, bound the Src-family kinase Lyn and linked TLR9 to a Src–kinase Syk–transcription factor STAT3 cascade essential for TLR9-driven B cell proliferation and differentiation. Thus, DOCK8 functions as an adaptor in a TLR9-MyD88 signaling pathway in B cells.

DNA repair gene XPD and XRCC1 polymorphisms and the risk of childhood acute lymphoblastic leukemia

Polymorphisms have been identified in several DNA repair genes. These polymorphisms may effect DNA repair capacity and modulate cancer susceptibility. In this study, we aimed to determine the four polymorphisms in two DNA repair genes, xeroderma pigmentosum complementation group D (XPD) and X-ray repair cross-complementing group 1 (XRCC1), in a sample of Turkish patients with childhood acute lymphoblastic leukemia (ALL), and evaluate their association with childhood ALL development. We used polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP), to analyze XPD Asp312Asn, XPD Lys751Gln, XRCC1 Arg194Trp, and XRCC1 Arg399Gln polymorphisms in 70 patients with childhood ALL and in 75 disease-free controls, who were of a similar age. No significant differences were observed among the study groups with regard to the XPD codon 312, XPD codon 751, XRCC1 codon 194, and XRCC1 codon 399 polymorphisms. However, the combined XRCC1 Arg194Trp/Trp194Trp variant genotypes were associated with increased risk for ALL in females (OR=5.47; 95% CI=1.49-20.10; p=0.008). This finding indicates that females carrying XRCC1 194Trp allele are at increased risk of developing childhood ALL. These results suggest that the risk of childhood ALL may be associated with DNA repair mechanisms, and understanding these mechanisms will help identify individuals at increased risk of developing childhood ALL, and also should be lead to improved treatment of ALL.

Clinical variability of asphyxiating thoracic dystrophy (Jeune) syndrome: Evaluation and classification of 13 patients.

Asphyxiating thoracic dystrophy‐Jeune syndrome (JS) is a rare autosomal recessive disease characterized by small thorax and short limb dwarfism. Besides the clinical variability, prognosis also differs greatly among patients. Pulmonary involvement is predominant in some cases whereas renal involvement is much more evident in others. We aimed to investigate the clinical variability and prognosis in 13 patients with JS from 11 families. Two of them, who had been diagnosed in the prenatal period were assessed by autopsy findings. All patients had a bell‐shaped or long narrow short thorax and brachydactyly at varying degrees from mild to severe. Short stature was common feature emerging in the postnatal period. One patient had atlantoaxial instability and spinal cord compression which have not been reported in JS before. In the postnatal follow up of 11 patients, respiratory distress was observed in eight patients and proved lethal in six, one patient died of chronic renal failure, and the remaining four patients were still alive at the end of the study. Patients were classified into three groups consisting of severe pulmonary involvement, renal involvement, and mild form in terms of prognosis. Patients with severe pulmonary involvement had bell‐shaped thorax and mild brachydactyly, the one patient with renal involvement had long narrow thorax and severe brachydactyly, and patients with mild involvement presented with polydactyly and moderate to severe brachydactyly. It is important to establish a correct diagnosis both in severe and mild forms since JS might recur within the same family.

Vitamin D as an adjunct to subcutaneous allergen immunotherapy in asthmatic children sensitized to house dust mite

We aimed to investigate the efficacy, safety, and T regulatory cell response of vitamin D as an adjunct to allergen‐specific immunotherapy (IT).

Outcome of hypogammaglobulinemia in children: Immunoglobulin levels as predictors

We evaluated 131 children (M=88, F=43) with hypogammaglobulinemia. Data was analyzed mainly for delineating predictor factors for outcome. The distance from the lower limit of normal (-2SD) for any single measurement of immunoglobulins (Ig) was calculated and transformed into Ig scores. Mean age and duration of follow-up were 5.06 ± 4.05 and 3.7 ± 3.03 years, respectively. The diagnoses were: 22 CVID, 16 IgA deficiency, 33 transient hypogammaglobulinemia of childhood (THC), 3 selective IgM deficiency and 57 unclassified hypogammaglobulinemia (UCH). Low IgA scores (<-0.124) at presentation were indicative of subsequent development of IgA deficiency or CVID, whereas low IgM score (<-0.038) pointed towards more severe and persistent phenotypes. Combination of low IgM score between 2 and 5 years, impaired antibody response and low B cell counts enabled us to predict persistence of hypogammaglobulinemia beyond 5 years (specificity=90.5% and PPV=94.9%) and chronic lung disease (sensitivity=90.4% and specificity=68.3%). The set of criteria including low IgM scores, impaired antibody response and low B cell counts provided a high predictive value in detecting those with persistent hypogammaglobulinemia.

CD55 Deficiency, Early-Onset Protein-Losing Enteropathy, and Thrombosis

Background Studies of monogenic gastrointestinal diseases have revealed molecular pathways critical to gut homeostasis and enabled the development of targeted therapies. Methods We studied 11 patients with abdominal pain and diarrhea caused by early‐onset protein‐losing enteropathy with primary intestinal lymphangiectasia, edema due to hypoproteinemia, malabsorption, and less frequently, bowel inflammation, recurrent infections, and angiopathic thromboembolic disease; the disorder followed an autosomal recessive pattern of inheritance. Whole‐exome sequencing was performed to identify gene variants. We evaluated the function of CD55 in patients’ cells, which we confirmed by means of exogenous induction of expression of CD55. Results We identified homozygous loss‐of‐function mutations in the gene encoding CD55 (decay‐accelerating factor), which lead to loss of protein expression. Patients’ T lymphocytes showed increased complement activation causing surface deposition of complement and the generation of soluble C5a. Costimulatory function and cytokine modulation by CD55 were defective. Genetic reconstitution of CD55 or treatment with a complement‐inhibitory therapeutic antibody reversed abnormal complement activation. Conclusions CD55 deficiency with hyperactivation of complement, angiopathic thrombosis, and protein‐losing enteropathy (the CHAPLE syndrome) is caused by abnormal complement activation due to biallelic loss‐of‐function mutations in CD55. (Funded by the National Institute of Allergy and Infectious Diseases and others.)

ASSOCIATION BETWEEN GENETIC POLYMORPHISM IN DNA REPAIR GENES AND RISK OF B-CELL LYMPHOMA

Objectives: The authors evaluated the possible effect of DNA repair genes, XPD (Xeroderma pigmentosum group D) codon (312 and 751) and XRCC1 (X-ray repair cross-complementing group 1) codon (194 and 399) SNPs (single-nucleotide polymorphisms) on the risk of childhood B-cell lymphoma. Methods: The polymorphisms were analyzed in 33 patients with BL cases and in 52 healthy, age-matched controls using PCR-RFLP method. Results: The authors observed no association between variation in the XPD codon Asp312Asn, Lys751Gln, and XRCC1 codon Arg399Gln polymorphisms and B-cell lymphoma for any parameter. In contrast, tryptophan allele frequency in control and patient groups was 0.10 and 0.03 respectively (p = .04). The frequency of XRCC1 194Arg/Trp genotype in B-cell lymphoma was significantly lower than that in controls (p = .005). No significant relationship was found between genotypes and stage, lactate dehydrogenase, or bone marrow involvement. Conclusions: XRCC1 194Trp allele may be associated with a protective effect against development of childhood B-cell lymphoma. However, these results were based on a small number of case and further studies should be done.

Potentially Beneficial Effect of Hydroxychloroquine in a Patient with a Novel Mutation in Protein Kinase Cδ Deficiency

Protein kinase C delta (PRKCD) has essential functions in controlling B-cell proliferation and apoptosis, development of B-cell tolerance and NK-cell cytolitic activity. Human PRKCD deficiency was recently identified to be causative for an autoimmune lymphoproliferative syndrome like disorder with significant B-cell proliferation particularly of immature B cells. Here we report a child with a novel mutation in PRKCD gene who presented with CMV infection and an early onset SLE-like disorder which was successfully treated with hydroxychloroquine.

DNA repair gene XPD and XRCC1 polymorphisms and the risk of febrile neutropenia and mucositis in children with leukemia and lymphoma

The aim of the study is to investigate association between DNA repair gene XPD and XRCC1 polymorphisms and febrile neutropenia (FN) and mucositis. The study population consisted of 29 children with Burkitt lymphoma and 61 children with acute lymphoblastic leukemia. Analysis revealed that XRCC1194Trp allele showed a protective effect against longer FN and mucositis. There was also statistically increased risk for severe mucositis in patients with XRCC1Arg399Gln polymorphism. There are no studies that have examined this relationship before. Further studies with larger cohorts are needed to clarify the association.

Exaggerated follicular helper T-cell responses in patients with LRBA deficiency caused by failure of CTLA4-mediated regulation

Background: LPS‐responsive beige‐like anchor protein (LRBA) and cytotoxic T lymphocyte–associated antigen 4 (CTLA4) deficiencies give rise to overlapping phenotypes of immune dysregulation and autoimmunity, with dramatically increased frequencies of circulating follicular helper T (cTFH) cells. Objective: We sought to determine the mechanisms of cTFH cell dysregulation in patients with LRBA deficiency and the utility of monitoring cTFH cells as a correlate of clinical response to CTLA4‐Ig therapy. Methods: cTFH cells and other lymphocyte subpopulations were characterized. Functional analyses included in vitro follicular helper T (TFH) cell differentiation and cTFH/naive B‐cell cocultures. Serum soluble IL‐2 receptor &agr; chain levels and in vitro immunoglobulin production by cultured B cells were quantified by using ELISA. Results: cTFH cell frequencies in patients with LRBA or CTLA4 deficiency sharply decreased with CTLA4‐Ig therapy in parallel with other markers of immune dysregulation, including soluble IL‐2 receptor &agr; chain, CD45RO+CD4+ effector T cells, and autoantibodies, and this was predictive of favorable clinical responses. cTFH cells in patients with LRBA deficiency were biased toward a TH1‐like cell phenotype, which was partially reversed by CTLA4‐Ig therapy. LRBA‐sufficient but not LRBA‐deficient regulatory T cells suppressed in vitro TFH cell differentiation in a CTLA4‐dependent manner. LRBA‐deficient TFH cells supported in vitro antibody production by naive LRBA‐sufficient B cells. Conclusions: cTFH cell dysregulation in patients with LRBA deficiency reflects impaired control of TFH cell differentiation because of profoundly decreased CTLA4 expression on regulatory T cells and probably contributes to autoimmunity in patients with this disease. Serial monitoring of cTFH cell frequencies is highly useful in gauging the clinical response of LRBA‐deficient patients to CTLA4‐Ig therapy.