Kenichi Koike

IL-9 Enhances the Growth of Human Mast Cell Progenitors Under Stimulation with Stem Cell Factor

We examined the effects of IL-9 on human mast cell development from CD34+ cord blood (CB) and peripheral blood cells in serum-deprived cultures. IL-9 apparently enhanced cell production under stimulation with stem cell factor (SCF) from CD34+ CB cells. A great majority of the cultured cells grown with SCF + IL-9 became positive for tryptase at 4 wk. In methylcellulose cultures of CD34+ CB cells, IL-9 increased both the number and size of mast cell colonies grown with SCF. Furthermore, SCF + IL-9 caused an exclusive expansion of mast cell colony-forming cells in a 2-wk liquid culture of CD34+ CB cells, at a level markedly greater than for SCF alone. Clonal cell cultures and RT-PCR analysis showed that the targets of SCF + IL-9 were the CD34+CD38+ CB cells rather than the CD34+CD38− CB cells. IL-9 neither augmented the SCF-dependent generation of progeny nor supported the survival of 6-wk-cultured mast cells. Moreover, there was no difference in the appearance of tryptase+ cells and histamine content in the cultured cells between SCF and SCF + IL-9. The addition of IL-9 increased numbers of mast cell colonies grown with SCF from CD34+ peripheral blood cells in children with or without asthma. It is of interest that mast cell progenitors of asthmatic patients responded to SCF + IL-9 to a greater extent than those of normal controls. Taken together, IL-9 appears to act as a potent enhancer for the SCF-dependent growth of mast cell progenitors in humans, particularly asthmatic patients.

Allogeneic hematopoietic stem cell transplantation for 27 children with juvenile myelomonocytic leukemia diagnosed based on the criteria of the International JMML Working Group.

Prognostic factors of juvenile myelomonocytic leukemia (JMML) have not been clarified because of its very low incidence and inaccuracy in the diagnosis. The purpose of this study was to evaluate children with JMML given an allogeneic hematopoietic stem cell transplantation (SCT) and the role of different variables potentially influencing outcome in a nationwide survey in Japan based on the newly proposed criteria by the International JMML Working Group. The study patients were 27 children who underwent SCT among 55 JMML patients retrospectively collected in the survey. The source of grafts was HLA-identical siblings in 12 cases, HLA-matched unrelated individuals in 10 and others in five. Total body irradiation was used in 18 cases. Event-free and overall survival (OS) at 4 years after SCT were 54.2 ± 11.2% (s.e.) and 57.9 ± 11.0% (s.e.), respectively. Six patients died of relapse and three of complications. Patients with abnormal karyotypes showed a significantly lower OS than those with normal karyotypes (P < 0.001). Patients below 1 year of age showed a significantly higher OS than those of 1 year of age or more (P = 0.02). Patients with grade 0–1 acute graft-versus-host disease (GVHD) or chronic GVHD had a more favorable OS than those without them, although they were not statistically significant (P > 0.05). Other variables studied were not associated with OS. A multivariate analysis of these factors yielded the abnormal karyotype as the only significant risk factor for lower OS (risk ratio: 11.0; 95% CI: 2.7–45.1).

Dynamic DNA methylation change in the CpG island region of p15 during human myeloid development

We examined the kenetics of p15 methylation and expression during myeloid development. We treated human cord blood CD34+ cells with either GM-CSF alone or in combination with stem cell factor and followed methylation at this locus using bisulfite genomic sequencing. CD34+ cells were found to be either fully methylated or completely unmethylated at 27 CpG dinucleotide sites in exon 1 and at 18 CpG sites in the promoter region of the p15 gene. A time-course study showed that the percentage of the allelic methylation of p15 CpG island increased to approximately 50% to 60% until 7 days after cytokine stimulation, then decreased to less than 10% after 21 days. The methylation was also observed in bone marrow CD34+ cells exposed to GM-CSF. p15 expression varied inversely with methylation. Expression was negligible or at low levels until 14 days, after which it increased substantially. The frequency of myeloid colony-forming cells in the progeny decreased and myeloid-specific markers increased in the later stages. Based on our observations on cells grown with GM-CSF and 5-aza-2-deoxycytidine, DNA methylation of the p15 promoter region CpG island appears to be associated with proliferation rather than differentiation of normal human myeloid progenitors.

Allogeneic haematopoietic cell transplantation from alternative donors with a conditioning regimen of low-dose irradiation, fludarabine and cyclophosphamide in Fanconi anaemia

A pilot study was undertaken using a fludarabine‐based conditioning regimen to improve haematopoietic cell transplantation (HCT) from alternative donors in 27 Fanconi anaemia (FA) patients. Patients were conditioned with 150–180u2003mg/m2 of fludarabine, 40u2003mg/kg of cyclophosphamide, 5–10u2003mg/kg of antithymocyte globulin, and 300–450u2003cGy of thoracoabdominal/total body irradiation. One patient who received unrelated cord blood transplantation failed to engraft, another patient died of sepsis. The 1‐year overall survival was 96·3% (95% CI, 89–100). This conditioning regimen exerted an immunosuppressive effect that enabled durable engraftment in alternative donor HCT without severe toxicity.

An Increase in Circulating Mast Cell Colony-Forming Cells in Asthma

We compared a potential to generate mast cells among various sources of CD34+ peripheral blood (PB) cells in the presence of stem cell factor (SCF) with or without thrombopoietin (TPO), using a serum-deprived liquid culture system. From the time course of relative numbers of tryptase-positive and chymase-positive cells in the cultured cells grown by CD34+ PB cells of nonasthmatic healthy individuals treated with G-CSF, TPO appears to potentiate the SCF-dependent growth of mast cells without influencing the differentiation into mast cell lineage. CD34+ PB cells from asthmatic patients in a stable condition generated significantly more mast cells under stimulation with SCF alone or SCF+TPO at 6 wk of culture than did steady-state CD34+ PB cells of normal controls. Single-cell culture studies showed a substantial difference in the number of SCF-responsive or SCF+TPO-responsive mast cell progenitors in CD34+ PB cells between the two groups. In the presence of TPO, CD34+ PB cells from asthmatic children could respond to a suboptimal concentration of SCF to a greater extent, compared with the values obtained by those of normal controls. Six-week cultured mast cells of asthmatic subjects had maturation properties (intracellular histamine content and tryptase/chymase enzymatic activities) similar to those derived from mobilized CD34+ PB cells of nonasthmatic subjects. An increase in a potential of circulating hemopoietic progenitors to differentiate into mast cell lineage may contribute to the recruitment of mast cells toward sites of asthmatic mucosal inflammation.

Serologic analysis of three cases of neonatal alloimmune thrombocytopenia associated with HLA antibodies

BACKGROUND: Neonatal alloimmune thrombocytopenia (NAIT) is caused when maternal alloantibodies react with paternally inherited antigens present on the fetal PLTs, a reaction mainly due to antibodies against human PLT antigens. Cases in which NAIT has been caused by HLA antibodies are relatively rare. In this study, three cases of NAIT associated with HLA antibodies that occurred in a 1‐year period are reported.

Methylation status of the p15 and p16 genes in paediatric myelodysplastic syndrome and juvenile myelomonocytic leukaemia

Aberrant DNA methylation is frequently observed in adults with myelodysplastic syndrome (MDS), and is recognized as a critical event in the diseases pathogenesis and progression. This is the first report to investigate the methylation status of p15 and p16, cell cycle regulatory genes, in children with MDS (nu2003=u20039) and juvenile myelomonocytic leukaemia (JMML; nu2003=u200318) by using a methylation‐specific polymerase chain reaction. The frequency of p15 hypermethylation in paediatric MDS was 78% (7/9), which was comparable to that in adult MDS. In contrast, p15 hypermethylation in JMML was a rare event (17%; 3/18). In JMML, clinical and laboratory characteristics including PTPN11 mutations and aberrant colony formation were not different between the three patients with hypermethylated p15 and the others. Aberrant methylation of p16 was not detected in children with either MDS or JMML. Since p15 and p16 genes were unmethylated in two children with JMML, in whom the disease had progressed with an increased number of blasts, a condition referred to as blastic crisis, we infer that the aberrant methylation of these genes is not responsible for the progression of JMML. The results suggest that demethylating agents may be effective in most children with MDS and a few patients with JMML.

Treatment of neurodegenerative CNS disease in Langerhans cell histiocytosis with a combination of intravenous immunoglobulin and chemotherapy.

In rare cases, patients with Langerhans cell histiocytosis (LCH) develop neurodegenerative CNS disease (ND‐CNS‐LCH). Management of ND‐CNS‐LCH has not been established.

STI571 inhibits growth and adhesion of human mast cells in culture

Stem cell factor (SCF)/c‐kit system is critical for human mast cell development. We thus examined the effects of STI571, an inhibitor of the c‐kit tyrosine kinase receptor, on the proliferation and function of human mast cells. STI571 at concentrations of 10−6 M or higher almost completely abolished the SCF‐dependent progeny generation from cord blood‐derived cultured mast cells through an inhibition of the tyrosine phosphorylation of c‐kit. The compound also suppressed the early phase of mast cell development. The extinction of mast cell growth induced by STI571 may be due largely to apoptosis according to the flow cytometric analysis and gel electrophoresis. Two‐hour exposure to STI571 that failed to influence the total viable cell number suppressed adhesion of the cells to fibronectin in the presence of SCF without altering the expressions of integrin molecules. Our results may provide a fundamental insight for the clinical application of STI571 in allergic disorders.

Serum inhibitors for human mast cell growth: possible role of retinol

Background: In vitro culture systems have been used to study the physiological and pathological characteristics of human mast cells. However, there are some differences in proliferation and maturation of mast cells between fetal bovine serum (FBS)‐containing and serum‐deprived cultures. Accordingly, we attempted to identify circulating factor(s) affecting the development of human mast cells.