A case of thrombomodulin mutation causing defective thrombin binding with absence of protein C and TAFI activation.

Thrombomodulin functions as an anticoagulant through thrombin binding and protein C activation. We herein report the first case of hereditary functional thrombomodulin deficiency presenting with recurrent subcutaneous hemorrhage and old cerebral infarction. The patient had a homozygous substitution of glycine by aspartate at amino acid residue 412 (Gly412Asp) in the thrombin-binding domain of the thrombomodulin gene (designated thrombomodulin-Nagasaki). In vitro assays using a recombinant thrombomodulin with the same mutation as the patient showed a total lack of thrombin binding and activation of protein C and thrombin-activatable fibrinolysis inhibitor (TAFI). Marked clinical and laboratory improvement was obtained with recombinant human soluble thrombomodulin therapy.

Interferon regulatory factor 4 differentially regulates the production of Th2 cytokines in naive vs. effector/memory CD4+ T cells.

Interferon regulatory factor (IRF) 4 is a member of the IRF family of transcription factors and plays critical roles in the development of CD4(+) T cells into Th2 and Th17 cells. Using the infection model of Nippostrongyrus brasiliensis, we have confirmed the critical roles of IRF-4 in Th2 development in vivo by using IRF-4(-/-) BALB/c mice. However, naïve IRF-4(-/-)CD4(+) T cells produced Th2 cytokines, including IL-4, IL-5, and IL-10, but not IL-2 or IFN-gamma, at levels higher than wild-type BALB/c CD4(+) T cells in response to T cell receptor stimulation. In contrast, effector/memory IRF-4(-/-)CD4(+) T cells did not exhibit increased production of Th2 cytokines. Knockdown of IRF-4 expression by using small interfering RNA promoted IL-4 production in naïve CD4(+) T cells but inhibited it in effector/memory CD4(+) T cells. These results indicate that IRF-4 plays differential roles in the regulation of Th2 cytokine production in naïve CD4(+) T cells and effector/memory CD4(+) T cells. IRF-4 inhibits Th2 cytokine production in naïve CD4(+) T cells, whereas it promotes Th2 cytokine production in effector/memory CD4(+) T cells.

TT virus prevalence, viral loads and genotypic variability in saliva from healthy Japanese children.

AIM: TT virus (TTV) is genetically variable and widespread without apparent pathogenicity; however, its epidemiological features in children were not fully understood, partly because blood sampling is often unacceptable for healthy children. We therefore used saliva specimens to investigate epidemiology of TTV infection in early childhood. METHODS: Saliva samples were collected from 83 1-month-old, 110 4-month-old and 49 42-month-old children. Peripheral blood mononuclear cells (PBMC) and saliva samples were obtained in pairs from 19 healthy adults aged 40 +/- 7 years. TTV DNA was detected and quantified by real-time PCR and classified into five genogroups (G1-G5) by a series of PCRs using genogroup-specific primer pairs. RESULTS: TTV DNA was detected in 6, 34 and 90% of children aged 1, 4 and 42 months, respectively, and in 84% of adults. Comparable levels of TTV DNA were detected in pairs of saliva and PBMC. TTV loads in saliva were much higher in children than in adults. G3 was the most common genogroup in all age groups. The second most prevalent was G4 at 1-4 months of age and G1 thereafter. CONCLUSION: The prevalence of TTV infection reached a plateau at or before 42 months; however, somehow different epidemiologic features were observed among genogroups.

Severe postnatal cytomegalovirus infection in a very premature infant.

Several studies have reported that postnatally acquired cytomegalovirus (CMV) infection can cause sepsis-like syndrome in premature infants. We here report a 622-gram birth weight male infant of 23 weeks' gestation who had sepsis-like syndrome and pneumonia. Substantial CMV loads were detected in peripheral blood cells, plasma, and urine when the patient was in crisis, but was decreased in parallel to clinical improvement without using ganciclovir. CMV DNA was not detected from his umbilical cord or Guthrie card, even by highly sensitive real-time PCR. Molecular profiles were indistinguishable between the CMV strain isolated from his urine and that from maternal breast milk, indicating postnatal acquisition of CMV through breast milk. Although he had transient hearing impairment, his neurodevelopmental outcome of 30 months of corrected age was normal. Further accumulation of clinical and virological data in postnatal CMV infection is necessary for evaluating the severity and selecting patients requiring antiviral therapy.

Regulation of the maintenance of peripheral T-cell anergy by TAB1-mediated p38 alpha activation.

In anergic T cells, T-cell receptor (TCR)-mediated responses are functionally inactivated by negative regulatory signals whose mechanisms are poorly understood. Here, we show that CD4(+) T cells anergized in vivo by superantigen Mls-1(a) express a scaffolding protein, transforming growth factor beta-activated protein kinase 1-binding protein 1 (TAB1), that negatively regulates TCR signaling through the activation of mitogen-activated protein kinase p38 alpha. TAB1 was not expressed in naive and activated CD4(+) T cells. Inhibition of p38 activity in anergic T cells by a chemical inhibitor resulted in the recovery of interleukin 2 (IL-2) and the inhibition of IL-10 secretion. T-cell hybridoma 2B4 cells transduced with TAB1-containing retrovirus (TAB1-2B4 cells) showed activated p38 alpha, inhibited extracellular signal-regulated kinase (ERK) activity, culminating in reduced IL-2 levels and increased IL-10 production. The use of a p38 inhibitor or cotransfection of a dominant-negative form of p38 in TAB1-2B4 cells resulted in the recovery of ERK activity and IL-2 production. These results imply that TAB1-mediated activation of p38 alpha in anergic T cells regulates the maintenance of T-cell unresponsiveness both by inhibiting IL-2 production and by promoting IL-10 production.

Development of Th1 and not Th2 immune responses in mice lacking IFN-regulatory factor-4.

IFN-regulatory factor (IRF)-4 is a member of the IRF family of transcription factors expressed in lymphocytes and macrophages. The previous studies using mice deficient in the IRF-4 gene showed profound defects in function of both B and T cells. To further investigate the role of IRF-4 in CD4(+) T cell function, IRF-4(-/-) mice were challenged with the intracellular pathogen Leishmania major. The mice were protected against L. major during the early phase of the infection and CD4(+) T cells of the infected mice produced IFN-gamma in response to L. major antigen. However, during the late phase of infection, lymphocyte numbers were dramatically reduced in the draining lymph nodes, resulting in the deterioration of the lesion, indicating that IRF-4 was required for sustained immune responses against L. major infection. The function of CD4(+) T cells was further investigated using TCR transgenic mice lacking the IRF-4 gene. CD4(+) T cells from IRF-4(-/-) mice produced IFN-gamma and expressed T-bet after culture under T(h)1-skewing conditions in vitro. However, T(h)2 cell development was not observed after culture under T(h)2-polarizing conditions. Proliferation of CD4(+) T cells to IL-4 was reduced in IRF-4(-/-) mice, suggesting the defects in the responsiveness to IL-4. Furthermore, stimulation of the IRF-4(-/-) CD4(+) T cells with IL-4-induced activation of signal transducer and activator of transcription 6, but not expression of growth factor independent-1. Thus, development of CD4(+) T cell subsets differentially depends on IRF-4; induction of T(h)1 response does not depend on IRF-4, while T(h)2 response depends entirely on IRF-4.