Masahiro Hirayama

A Pivotal Role of Rho GTPase in the Regulation of Morphology and Function of Dendritic Cells

Dendritic cell (DC) is the most potent activator of CD4+ T cells and has unique dendrites and veils. To explore the function of Rho in DC, exoenzyme C3 from Clostridium botulinum was used as a specific inhibitor of Rho. Treatment of DC with C3 (DC/C3) resulted in profound morphological changes by losing dendrites and emerging of shrunk membrane processes that were in parallel with marked reduction of polymerized actin in the marginal area. Inactivation of Rho-associated coiled coil-containing kinase (p160ROCK) by a specific ROCK inhibitor Y-27632 also led to disappearance of dendrites of DC with retaining large membrane expansions. In scanning electron microscopy, untreated DCs interacted with CD4+ T cells more efficiently than DC/C3. Conjugate formation assay showed that the number of DCs associated with CD4+ T cells was 2-fold higher in untreated DCs than that of DC/C3. Alloantigen-presenting capacity of DC/C3 was significantly suppressed in a dose-dependent manner. Because C3 treatment did not affect the surface expression of HLA, costimulatory, and adhesion molecules of DC, we examined cytokine production of DC and naive CD4+ T cells to further elucidate the inhibitory mechanism of MLR. Unexpectedly, DC/C3 increased IL-12 production after LPS stimulation. Naive CD4+ T cells cocultured with DC/C3 produced the increased percentage of IFN-γ-producing cells, whereas the percentage of IL-2-producing T cells was decreased. These results demonstrate that Rho GTPase in DC controls both characteristic shape and immunogenic capacity.

BK virus-associated fatal renal failure following late-onset hemorrhagic cystitis in an unrelated bone marrow transplantation.

The human polyomavirus BK (BKV)-associated hemorrhagic cystitis (HC) has been a frequent and seldom life-threatening complication after bone marrow transplantation (BMT). The authors report a male with myelodysplastic syndrome, who developed BKV-associated late-onset HC 12 days after HLA-matched unrelated BMT. His urine contained epithelial cells with intranuclear inclusion bodies suggestive of BKV infection and was positive for BKV in polymerase chain reaction. He did not respond to any treatment for HC. In addition, he developed BKV-associated acute renal failure on day 26, followed by hepatic veno-occlusive disease on day 42. This is the first case in which BKV may be associated with fatal progressive renal failure.

Viral load in Epstein-Barr virus-associated hemophagocytic syndrome

The viral load in peripheral blood from patients with Epstein‐Barr virus (EBV)‐associated hemophagocytic syndrome was measured by real‐time quantitative PCR and compared with that in infectious mononucleosis. Patients with EBV‐associated hemophagocytic syndrome generally had larger viral burdens, although it was difficult to differentiate EBV‐associated hemophagocytic syndrome from infectious mononucleosis simply by viral load. The difference in viral load seemed to be clearer in peripheral blood mononuclear cells than in plasma.

Two cytotoxic pathways of natural killer cells in human cord blood: implications in cord blood transplantation

Using K562 cells as a target we investigated cord blood (CB)–natural killer (NK) cytolytic pathways. The cytotoxicity of fresh CB‐NK cells was significantly lower than that of peripheral blood mononuclear cells (PB MNCs). When CB was incubated with IL‐2, the level of CB‐NK cytotoxicity was increased and boosted to the level observed in PB‐NK cells. Fresh CB‐NK cells induced apoptosis in target cells. Activated CB cells induced apoptosis and necrosis in target cells, at the same level as PB MNCs. CB stem cell transplantation may also induce graft‐versus‐host disease (GVHD)/graft‐versus‐leukaemia (GVL), similar to bone marrow transplantation.

Too young to talk of vertigo

In April, 2003, a previously healthy 5-year-old girl came to our hospital, with vomiting and abdominal pain. She had been vomiting several times an hour, for 8 h; the vomit did not contain blood or bile. Her medical and family histories were unremarkable; growth and developmental milestones were normal. The girl was alert and afebrile; heart rate and blood pressure were normal. General and neurological examination showed no abnormality. We diagnosed gastroenteritis, and prescribed intravenous fl uids. The girl stopped vomiting the next day, and was discharged the day after. However, she subsequently had several similar episodes of illness. On each occasion, she vomited for several hours, was treated with bed rest or intravenous fl uids, and recovered fully within a day; treatment with domperidone was ineff ective. Vomiting was often accompanied by abdominal pain and headache, but not by fever, cough, diarrhoea, or weight loss. Routine blood tests, including concentrations of glucose and ammonia, showed no abnormalities; nor did blood-gas testing. We sometimes found mild ketonuria. We found no abnormalities on electrocardiography, abdominal radiography or ultrasonography, CT of the abdomen and brain, or electroencephalography. We therefore provisionally diagnosed her illness as cyclic vomiting. 13 months after the fi rst episode, the girl’s mother revealed that before vomiting began, the patient often described feeling her head swaying. We surmised that this might be vertigo. Otoscopy showed nothing abnormal. We observed no nystagmus when the patient was at rest; reactive nystagmus was elicted from caloric refl ex testing (with warm and cold water) of the left ear, but not the right ear, implying damage to the semicircular canals of the right ear, or their aff erent nerves. Pure-tone audiometry showed mild sensorineural hearing loss in the right ear (fi gure). Ear-targeted CT showed no abnormalities. We therefore diagnosed Meniere’s disease, according to standard criteria, surmising that perhaps the patient was too young to complain of tinnitus or a sensation of aural fullness. We prescribed isosorbide, an osmotic diuretic; the patient’s vomiting and feeling of dizziness disappeared. A year after treatment started, we noted that her hearing had improved. When last seen, in June, 2008, the patient continued to be free of vomiting and vertigo; she continued to take isosorbide. Meniere’s disease, fi rst described in 1861, is idiopathic endolymphatic hydrops (excess fl uid in the inner ear), causing deafness, tinnitus, and vertigo. The median time of onset is the fourth decade; Meniere’s disease is rare in children. It is also probably underdiagnosed. Children who complain of dizziness tend to be overlooked, perhaps partly because they have diffi culty describing it, and because vaguely defi ned “dizziness” has many possible causes. Therefore, children with Meniere’s disease often present with vomiting—which can easily be misdiagnosed as cyclic vomiting or migraine (including abdominal migraine). Hearing loss sometimes develops after onset of the disease. Audiometry can be useful in identifying the cause of unexplained vomiting or “dizziness”; regrettably, it is not always widely available.

Polycythemia and Paraganglioma With a Novel Somatic HIF2A Mutation in a Male

Recently, a new syndrome of paraganglioma, somatostatinoma, and polycythemia has been discovered (known as Pacak–Zhuang syndrome). This new syndrome, with somatic HIF2A gain-of-function mutations, has never been reported in male patients. We describe a male patient with Pacak–Zhuang syndrome who carries a newly discovered HIF2A mutation. Congenital polycythemias have diverse etiologies, including germline mutations in the oxygen-sensing pathway. These include von Hippel–Lindau (Chuvash polycythemia), prolyl hydroxylase domain–containing protein-2, and hypoxia-inducible factor-2α (HIF-2α). Somatic gain-of-function mutations in the gene encoding HIF-2α were reported in patients with paraganglioma and polycythemia and have been found exclusively in female patients. Through sequencing of the HIF2A using DNA from paraganglioma in 15-year-old male patient, we identified a novel mutation of HIF2A: a heterozygous C to A substitution at base 1589 in exon 12 of HIF2A. The mutation was not found in germline DNA from leukocytes. The C1589A mutations resulted in substitution of alanine 530 in the HIF-2α protein with glutamic acid. This mutation is undoubtedly associated with increased HIF-2α activity and increased protein half-life, because it affects the vicinity of the prolyl hydroxylase target residue, proline 531. To our knowledge, this is the first report describing Pacak–Zhuang syndrome with somatic gain-of-function mutation in HIF2A in a male patient. Congenital polycythemia of unknown origin should raise suspicion for the novel disorder Pacak–Zhuang syndrome, even in male patients.

Tolerogenic effect of non-inherited maternal antigens in hematopoietic stem cell transplantation

Major histocompatibility complex antigens that provoke severe transplant reactions are referred to as the human leukocyte antigen (HLA) in human and as the H-2 in mice. Even if the donor and recipient are HLA-identical siblings, graft-versus-host reactions have been linked to differences in the minor histocompatibility antigen. As the chance of finding an HLA-identical sibling donor is only 25%, attention has been focused on using alternative donors. An HLA-mismatched donor with non-inherited maternal antigens (NIMA) is less immunogenic than that with non-inherited paternal antigens, because the contact between the immune systems of the mother and child during pregnancy affects the immune response of the child against NIMA. However, the immunologic effects of developmental exposure to NIMA are heterogeneous, and can be either tolerogenic or immunogenic. We recently have devised a novel method for predicting the tolerogenic effect of NIMA. In this review, we overview the evidence for the existence of the NIMA tolerogenic effect, the possible cellular and molecular basis of the phenomenon, and its utilization in hematopoietic stem cell transplantation. We suggest a future direction for the safe clinical use of this phenomenon, fetomaternal tolerance, in the transplantation field.

Prediction of Reactivity to Noninherited Maternal Antigen in MHC-Mismatched, Minor Histocompatibility Antigen-Matched Stem Cell Transplantation in a Mouse Model

The immunologic effects of developmental exposure to noninherited maternal Ags (NIMAs) are quite variable. Both tolerizing influence and inducing alloreaction have been observed on clinical transplantation. The role of minor histocompatibility Ags (MiHAs) in NIMA effects is unknown. MiHA is either matched or mismatched in NIMA-mismatched transplantation because a donor of the transplantation is usually limited to a family member. To exclude the participation of MiHA in a NIMA effect for MHC (H-2) is clinically relevant because mismatched MiHA may induce severe alloreaction. The aim of this study is to understand the mechanism of NIMA effects in MHC-mismatched, MiHA-matched hematopoietic stem cell transplantation. Although all offsprings are exposed to the maternal Ags, the NIMA effect for the H-2 Ag was not evident. However, they exhibit two distinct reactivities, low and high responder, to NIMA in utero and during nursing depending on the degree of maternal microchimerism. Low responders survived longer with less graft-versus-host disease. These reactivities were correlated with Foxp3 expression of peripheral blood CD4+CD25+ cells after graft-versus-host disease induction and the number of IFN-γ–producing cells stimulated with NIMA pretransplantation. These observations are clinically relevant and suggest that it is possible to predict the immunological tolerance to NIMA.

Outcome of recurrent or refractory acute lymphoblastic leukemia in infants with MLL gene rearrangements: A report from the Japan infant leukemia study group

Despite the poor outcome of recurrent or refractory acute lymphoblastic leukemia (ALL) in infants with MLL gene rearrangement, few studies have focused on this specific group. We conducted a retrospective analysis of infants with recurrent or refractory ALL from two previous consecutive Japanese studies to clarify the characteristics and prognostic factors among these patients

Functional immaturity of cord blood monocytes as detected by impaired response to hepatocyte growth factor.

Abstract Background : Monocytes as antigen‐presenting cells play an important role in host defense and transplantation. However, there are little reports on cord blood monocytes, and the role of monocytes in cord blood transplantation is largely unknown.