In vitro analysis of allogeneic lymphocyte interaction. I. Characterization and cellular origin of an Ia-positive helper factor- allogeneic effect factor

A soluble allogeneic effect factor (AEF) was produced by using H-2 congenic mouse strains and a serum.free cell culture medium. An AEF derived from untreated activated responder cells and irradiated stimulator cells provided helper cell function in a primary and secondary antibody response for both T-cell-depleted responder B cells and stimulator B cells. This interaction may be determined by genes situated in the I-A and I-B regions: additional K-region control was not excluded. Ia antigens, but neither H-2 nor Ig determinants are molecular constituents of AEF. The active components of this AEF consist, in part, of Ia antigens derived from both the activated responder cell population and irradiated stimulator cell population. An AEF derived from Ia negative responder cells and irradiated T-cell- depleted stimulator cells helps a secondary antibody response of T-cell- depleted stimulator B cells but not responder B cells. This genetically restricted AEF contains Ia antigens determined by the stimulator haplotype but not the responder haplotype. The priming antigen, DNP- keyhole limpet hemocyanin, is not a component of restricted AEF. The data suggest that restricted AEF may be a product of a stimulator B cell and/or macrophage. They support the hypothesis that the recognition by allogeneic T cells of Ia antigens on B cells activates the B cell to IgG antibody production

Microsatellite instability and mismatch repair gene mutations are common in young colorectal cancer patients in Hong Kong

Conference Theme: Challenges to Specialists in the 21st centurypublished_or_final_versio

Primary immunodeficiency in Hong Kong and the use of genetic analysis for diagnosis

Objectives. To review the management of primary immunodeficiency and discuss recent advances in genetic analysis. Design. Retrospective study. Setting. University teaching hospital, Hong Kong. Patients. Children diagnosed with primary immunodeficiency and followed up in the immunology clinic during the period 1988 to 2003. Main outcome measures. Demographic data, co-morbidities and treatment of patients, outcome and complications; identification of disease by genetic mutations. Results. Medical records of a total of 117 patients (72 male, 45 female) diagnosed with primary immunodeficiency in the Department of Paediatrics and Adolescent Medicine, Queen Mary Hospital, Hong Kong during the past 15 years (1988-2003) were reviewed. All patients were followed up in the immunology clinic. Some patients had been referred from the private sector or other hospitals for immunological workup. Six categories of primary immunodeficiency were identified: predominantly humoral defect (n=50), predominantly cellular defect (n=22), combined humoral and cellular defect (n=5), phagocytic defect (n=18), complement disorders (n=4), and others (n=18). Although infection was the underlying cause of most co-morbidities and mortality, autoimmune (n=7) and allergic (n=23) manifestations were common. In addition, three patients developed lymphoma. Recent advances in the genetic diagnosis of several types of primary immunodeficiency were also reviewed: X-linked Wiskott-Aldrich syndrome, X-linked chronic granulomatous disease, X-linked agammaglobulinaemia, X-linked lymphoproliferative syndrome, leukocyte adhesion disease type I, and X-linked hyperimmunoglobulin M syndrome. This provides an invaluable means of understanding the molecular basis of primary immunodeficiency and has important clinical applications. Conclusions. Co-morbidities like autoimmune disease and allergic disease are common in patients with primary immunodeficiency and should be carefully evaluated. Likewise, a diagnosis of primary immunodeficiency should be considered when evaluating patients with these conditions. Rapid progress in the field of molecular genetics will enable definite and early diagnosis, and more importantly, potential curative therapy to be administered.published_or_final_versio

Superfluid vs Ferromagnetic Behaviour in a Bose Gas of Spin-1/2 Atoms

We study the thermodynamic phases of a gas of spin-1/2 atoms in the Hartree-Fock approximation. Our main result is that, for repulsive or weakly-attractive inter-component interaction strength, the superfluid and ferromagnetic phase transitions occur at the same temperature. For strongly-attractive inter-component interaction strength, however, the ferromagnetic phase transition occurs at a higher temperature than the superfluid phase transition. We also find that the presence of a condensate acts as an effective magnetic field that polarizes the normal cloud. We finally comment on the validity of the Hartree-Fock approximation in describing different phenomena in this system.Comment: 10 pages, 2 figure

Molecular Diagnosis for Paediatric Genetic Disorders Using Whole Exome Sequencing of the Next Generation Sequencing Technology

Oral PresentationMolecular diagnosis for paediatric genetic diseases is important for targeted or tailored treatment, more informative genetic counselling and guiding the families for prenatal or pre-implantation diagnosis. Traditionally, linkage analysis using large multiplex families or multiple families with the same molecular cause is essential and the process could take years before a diagnosis can be reached. Candidate gene screening is usually the only method available for clinical laboratories for genetic diseases in Hong Kong. Next generation sequencing technology has virtually revolutionised the way genetic studies are conducted and provides opportunities for molecular diagnosis for genetic disorders that were never available before. With the possibility of sequencing the whole genome or almost all the coding exons of the genome, the method does not require the availability of large, multiple affected families and prior knowledge of candidate causal genes. It can be applied to a single patient or, as a usual practice, whole genome or whole exome sequencing for the patient plus parents. For whole exome sequencing (WES), it usually produces up to 100 million short sequencing reads of usually 100bp long. These short reads were firstly compared with sequences of a reference human genome and mapped to genomic regions from which they were generated. Each position (base pair) of a coding exon is usually covered with dozens to hundreds of sequencing reads. Analysing the sequences of these reads allows for identification of mutations that are different from the reference sequences. For WES for a single individual, up to 100,000 variants can be identified, with some of which are common variants in a population and some of which rare or private. The population frequencies of these variants are looked up in public databases such as those from the 1000 Genome Project or ESP6500, a project that sequenced 6500 individuals in the US. An internal database is also established with WES data from 200 samples from the local population. For rare, severe genetic disorders that are likely to be caused by mutations from a single gene, we can safely rule out the common (>1% in a population) variants and only focus on the rare or private variants. The nature of the mutations, such as with or without amino acid changes, changes in the open reading frame of the protein, the nature of the amino acid changes (similarity of the amino acid changed to), the conservation of this amino acid in different species, and the function of the gene in relationship to the disease phenotype, are considered to help pinpoint the causal mutations. We will present examples on using WES for molecular diagnosis for paediatric genetic disorders in our Department. These include detection of de novo mutations (mutations that are not detected in parents), somatic mutations and compound heterozygous mutations, and mutations missed by traditional laboratory testing, which demonstrated the power of this new technology in providing accurate molecular diagnosis.published_or_final_versio

Chronic benign neutropenia among Chinese children

Objective. To delineate the clinical behaviour of chronic benign neutropenia in Chinese children in Hong Kong. Design. Retrospective study. Setting. University teaching hospital, Hong Kong. Patients. All infants and children with absolute neutrophil count of 1.5 × 109 /L or lower for more than 3 months. Main outcome measures. Development of significant infection, and achievement of remission. Results. Twenty-four children with chronic benign neutropenia were identified between 1992 and 2001. Their median age of diagnosis was 9 months. The mean (standard deviation) initial absolute neutrophil count was 0.28 × 109 /L (0.24 × 109 /L). Twenty-three patients presented with infection. Of the 19 patients tested, four (21%) were positive for anti-neutrophil antibodies. Bone marrow examination was performed in 17 patients: nine had normal results, but six showed evidence of peripheral consumption, one showed late maturation arrest at band stage, and one showed phagocytosis of myeloid cells by histiocytes. The overall hospitalised infection rate was 51.6 episodes per 1000 patient-months. Ten percent of cases were considered 'significant' infections and required hospital admission with either surgical intervention or intravenous therapy (antibiotics or fluid replacement). In the first year of diagnosis, more than 80% of patients had their lowest absolute neutrophil count (mean, 0.16 × 109 /L; standard deviation, 0.11 × 109 /L). Granulocyte-colony stimulating factor was used to treat three patients and induced transient elevation of absolute neutrophil count in all three. The projected remission rate was 55.4% at 3 years. Even for those with persistent disease, there was significant recovery in absolute neutrophil count to a mean of 0.5 × 109 /L (P<0.01). Conclusions. Patients with chronic benign neutropenia experienced a relatively benign clinical course regardless of their remission status. Only a small proportion of patients developed significant infections. A multi-centre prospective study may help identify predictive factors of remission.published_or_final_versio

Autosomal Dominant Gain-of-function STAT1 Mutation is a Novel Genetic Etiology of Penicillium Marneffei Infection

Symposium / Free Paper 4: ImmunologyConference Theme: Inflammatory Basis of Perinatal and Childhood DiseasesBackground: Penicillium marneffei infection is indigenous to Southeast Asia. Majority of cases occur in patients with AIDS and secondary immunodeficiencies. We previously reported 4 HIV-negative children with chronic mucocutaneous candidiasis (CMC) and severe penicilliosis. Hyper-IgE syndrome was diagnosed in one of them, but extensive genetic studies on IL12-IFNγ axis, CARD9 and AIRE were unrevealing for the rest. Recently, STAT1 hyperphosphorylation causing defective Th1 and Th17 immunity is recognized as a cause of CMC. Objective: To investigate the genetic and functional defects of STAT1 signaling in children affected by penicilliosis. Methods: Targeted sequencing of STAT1 gene or total exome sequencing was performed in 3 patients with CMC and penicilliosis. PBMCs were isolated from patients and normal controls. Intracellular STAT1 phosphorylation (pSTAT1) towards interferon-α and interferon-γ stimulation was evaluated by flow cytometry. Cytokine production in PBMCs towards PMA and ionomycin stimulation was assessed. PBMCs were co-cultured with live Candida albicans and P. marneffei to evaluate interferon-γ response. Results: Heterozygous STAT1 missense mutations were identified in all 3 patients. Two mutations were located in the coiled-coil domain (P1 and P2) and one in the DNA-binding domain (P3). All 3 patients recovered from penicilliosis, but P1 eventually died of fulminant aspergillosis. The percentage of pSTAT1-positive PBMCs induced by interferon-α and interferon-γ was significantly higher in all 3 patients than normal controls, indicating that they had gain-of-function mutations. PBMCs from all patients displayed defective interferon-γ and interleukin-17 production towards PMA and PMA plus ionomycin, respectively. Interferon-γ production induced by C. albicans and P. marneffei in P2 was significantly lower than normal controls. Conclusions: For the first time, we demonstrated STAT1 gain-of-function mutation as an important and novel genetic etiology of invasive mycosis including penicilliosis and aspergillosis. Penicilliosis should be regarded as an indicator disease for primary immunodeficiencies in children without HIV infection unless proven otherwise.published_or_final_versio

Human oropharynx as natural reservoir of Streptobacillus hongkongensis

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Klebsiella infection in patients with thalassemia

Klebsiella infection has previously been reported in a few patients with transfusion-dependent thalassemia. The incidence and clinical spectrum of this infection in our cohort of patients were reviewed retrospectively. Among 160 patients observed for 12 years, there were 15 episodes of Klebsiella infection that occurred in 12 patients (7.5%), resulting in an incidence of 0.78 infections per 100 patient-years. The clinical spectrum included sinusitis (4 cases), intracranial infection (5 cases), septicemia (4 cases), and abscesses of the liver, lung, kidney, and parotid gland (1 case each). Three patients had recurrent infections involving different sites, 2 (16%) died of fulminant septicemia, and 3 (25%) had significant permanent neurological deficits. The antibiotic susceptibility pattern for the isolates was similar to the pattern for isolates recovered in the community. With regard to predisposing factors, iron overload and liver function derangement were found to be significant on univariate analysis (P = .046 and P = .049, respectively) but insignificant on multivariate analysis. Klebsiella infection was a serious and frequently encountered complication in our patients with transfusion-dependent thalassemia, resulting in high mortality and morbidity rates.published_or_final_versio