Satoru Kumaki

Cutting edge : the common gamma-chain is an indispensable subunit of the IL-21 receptor complex

The common γ-chain (γc) is an indispensable subunit of the functional receptor complexes for IL-4, IL-7, IL-9, and IL-15 as well as IL-2. Here we show that the γc is also shared with the IL-21R complex. Although IL-21 binds to the IL-21R expressed on γc-deficient ED40515− cells, IL-21 is unable to transduce any intracytoplasmic signals. However, in EDγ-16 cells, a γc-transfected ED40515− cell line, IL-21 binds to the IL-21R and can activate Janus kinase (JAK)1, JAK3, STAT1, and STAT3. The chemical cross-linking study reveals the direct binding of IL-21 to the γc. These data clearly demonstrate that the γc is an indispensable subunit of the functional IL-21R complex.

Hyper-IgM syndrome type 4 with a B lymphocyte–intrinsic selective deficiency in Ig class-switch recombination

Hyper-IgM syndrome (HIGM) is a heterogeneous condition characterized by impaired Ig class-switch recombination (CSR). The molecular defects that have so far been associated with this syndrome - which affect the CD40 ligand in HIGM type 1 (HIGM1), CD40 in HIGM3, and activation-induced cytidine deaminase (AID) in HIGM2 - do not account for all cases. We investigated the clinical and immunological characteristics of 15 patients with an unidentified form of HIGM. Although the clinical manifestations were similar to those observed in HIGM2, these patients exhibited a slightly milder HIGM syndrome with residual IgG production. We found that B cell CSR was intrinsically impaired. However, the generation of somatic hypermutations was observed in the variable region of the Ig heavy chain gene, as in control B lymphocytes. In vitro studies showed that the molecular defect responsible for this new HIGM entity (HIGM4) occurs downstream of the AID activity, as the AID gene was induced normally and AID-induced DNA double-strand breaks in the switch micro region of the Ig heavy chain locus were detected during CSR as normal. Thus, HIGM4 is probably the consequence of a selective defect either in a CSR-specific factor of the DNA repair machinery or in survival signals delivered to switched B cells.

Novel Artemis gene mutations of radiosensitive severe combined immunodeficiency in Japanese families

A subgroup of patients with severe combined immunodeficiency (SCID) and increased cellular radiation sensitivity (RS-SCID) have mutations of Artemis, a gene that encodes a protein essential for V(D)J recombination and DNA double-strand break repair. RS-SCID described to date are either of European origin or are Athabascan-speaking native Americans belonging to the Navajo and Apache tribes. We have identified three Japanese boys and one girl from four unrelated families with RS-SCID caused by a genomic exonxa03 deletion of the Artemis gene, resulting in loss of exonxa03 and skipping of exonxa04. Two patients were homozygous and two patients were heterozygous for this novel mutation. Those parents studied were heterozygous for this mutation. These findings suggest the genomic exonxa03 deletion is unique to Japan and may be considered as a founder haplotype. Although two infants underwent successful bone marrow transplantation and immune reconstitution, the long-term outcome of this procedure is uncertain, because Artemis is expressed in most tissues and lack of its function in cells other than those derived from hematopoietic stem cells may increase the risk of malignancies.

Flow cytometric determination of intracytoplasmic Wiskott–Aldrich syndrome protein in peripheral blood lymphocyte subpopulations

We have produced a novel monoclonal antibody (mAb) directed against Wiskott-Aldrich syndrome protein (WASP) by immunizing mice with the recombinant protein. The mAb designated 5A5 is highly specific to WASP and suitable for Western blot analysis and immunoprecipitation. A flow cytometric assay using the 5A5 mAb identifies expression of intracytoplasmic WASP in lymphocytes from normal individuals. Double staining analysis with cell surface CD3, CD19, and CD56, and intracytoplasmic molecules revealed WASP expression in each subpopulation. With regard to WASP expression in patients with Wiskott-Aldrich syndrome (WAS) and X-linked thrombocytopenia (XLT), peripheral blood mononuclear cells (PBMCs) from nine patients and Epstein-Barr virus-transformed B-lymphoblastoid cell lines from seven patients examined did not show WASP expression by flow cytometric analysis. These results were confirmed by Western blot analysis. We conclude that WASP expression in lymphocyte subpopulations from patients with WAS and XLT can be more precisely evaluated by flow cytometry as compared with Western blot analysis. This flow cytometry method is important as a supplement to Western blots, but even more important as an alternative and powerful assay that can contribute to research on WASP as well as diagnosis in a clinical setting.

Deficient activity of von Willebrand factor-cleaving protease in patients with Upshaw-Schulman syndrome.

We identified unusually large von Willebrand factor (vWF) multimers caused by deficient activity of vWF-cleaving protease in 2 patients with Upshaw-Schulman syndrome. The autoantibodies that inhibited the protease activity were not detected in the plasma of either patient. Periodic fresh-frozen plasma transfusion was effective for management of the hemolysis and thrombocytopenia. We detected enriched enzyme activity in a particular plasma fraction, although molecular cloning of this specific protease is needed to determine a more detailed pathogenesis and to develop new therapeutic approaches.

Successful umbilical cord blood transplantation from an unrelated donor for a patient with Epstein–Barr virus-associated hemophagocytic lymphohistiocytosis

We report a case of a 5-year-old girl with EBV-associated hemophagocytic lymphohistiocytosis (EBV-HLH) who underwent cord blood (CB) stem cell transplantation (CBSCT) from an unrelated donor. The patient presented with persistent high-grade fever and hepatosplenomegaly. Because the disease was refractory to immunochemotherapy according to the HLH94 protocol, she received 2.0 × 107 CB nucleated cells/kg body weight (BW) after conditioning with BU/CY/etoposide. No acute GVHD developed, using FK506 for prophylaxis. The neutrophil count reached >0.5 × 109/l by day 21 and the platelet count reached >50 × 109/l by day 84. The patient recovered well with sequelae of neurological deficits more than 10 months after receiving CBSCT, without showing evidence of HLH or chronic GVHD. Real-time PCR proved applicable for estimation of the EBV load in PBMC of the patient. We conclude that CBSCT may be indicated for some cases of refractory EBV-HLH, who have no HLA-matched siblings and are therefore dependent on unrelated marrow donors. Bone Marrow Transplantation (2001) 27, 883–886.

Epstein-Barr virus-associated hodgkin's disease in a patient with Wiskott-Aldrich syndrome.

Wiskott‐Aldrich syndrome is a primary immunodeficiency syndrome in which the majority of malignant complications are non‐Hodgkins lymphoma. We report here a Wiskott‐Aldrich syndrome patient who developed Epstein‐Barr virus‐positive Hodgkins disease in the bilateral pulmonary hilar lymph nodes. The treatment was successful as the patient achieved a complete response and event‐free survival for more than 4 y.

Refractory autoimmune hemolytic anemia in a patient with chromosome 22q11.2 deletion syndrome

The monosomic deletion of chromosomal segment 22q11.2 causes a disorder with a broad clinical spectrum and includes DiGeorge syndrome (DGS), conutruncal anomaly face syndrome (CAFS), velocardiofacial syndrome (VCSF), and isolated conutruncal heat defect. 1 The acronym ‘CATCH 22’ (Cardic defects, Abnormal facies, Thymic hypoplasia, Cleft palate, and Hypocalcemia resulting from a 22q11.2 deletion) has been proposed to describe the phenotype. The phenotypic spectrum of the 22q11.2 syndrome is widely variable, even among affected family members. 2,3 At present, there is no satisfactory explanation for the variability. Here we report an infant with 22q11.2 deletion syndrome who has tetratgy of Fallot, a T-cell deficiency, cleft palate, and hypocalcemia. In addition, this patient showed autoimmune hemolytic anemia (AIHA). It is suggested that AIHA might be part of the spectrum of clinical features associated with the 22q11.2 deletion syndrome.

A novel JAK3 mutation in a Japanese patient with severe combined immunodeficiency

Severe combined immunodeficiency (SCID) is a rare syndrome characterized by a profound impairment of both cellular and humoral immune responses. 1 A predominant form of SCID is X-linked SCID (X-SCID) caused by mutations in the IL2RG gene, coding the γ c chain, which is characterized by markedly diminished numbers of T and NK cells, and normal or elevated numbers of dysfunctional B cells (T-B+NK-SCID). An autosomal recessive SCID with clinical features similar to X-SCID has been reported as JAK3 deficiency. 2,3 JAK3 is the only tyrosine kinase known to be directly associated with the γ c chain, which is essential for signal transduction through γ c-containing receptors for interleukins 2, 4, 7, 9, 15 and 21. 1

DIDMOAD Syndrome (Wolfram Syndrome) in Four Male Siblings

Four male siblings including two typical cases of DIDMOAD syndrome are described. The typical cases were aged 16 and 15, with diabetes insipidus, insulin‐dependent diabetes mellitus (IDDM), optic atrophy, perceptive hearing loss, dilatation of the urinary tract and disturbed EEC One of the others was aged 10, with bilateral concentric limitation of the peripheral visual fields, retinal pigment degeneration and disturbed EEG, and the other was aged 6, with IDDM and perceptive hearing loss. The family history revealed complicated parental consanguinity, with some members suffering from diabetes mellitus and deafness. In our cases hereditary transmission seemed to be autosomal recessive, as previously described, and we could not find any association of this syndrome with HLA.