WNT signaling has been implicated in the regulation of hematopoietic stem cells and plays an important role during T-cell development in thymus. Here we investigated WNT pathway activation in childhood T-cell acute lymphoblastic leukemia (T-ALL) patients. To evaluate the potential role of WNT signaling in T-cell leukomogenesis, we performed expression analysis of key components of WNT pathway. More than 85% of the childhood T-ALL patients showed upregulated β-catenin expression at the protein level compared with normal human thymocytes. The impact of this upregulation was reflected in high expression of known target genes (AXIN2, c-MYC, TCF1 and LEF). Especially AXIN2, the universal target gene of WNT pathway, was upregulated at both mRNA and protein levels in ∼40% of the patients. When β-CATENIN gene was silenced by small interfering RNA, the cancer cells showed higher rates of apoptosis. These results demonstrate that abnormal WNT signaling activation occurs in a significant fraction of human T-ALL cases independent of known T-ALL risk factors. We conclude that deregulated WNT signaling is a novel oncogenic event in childhood T-ALL.

Pancytopenia, although mainly reported in adults, has also been described in children with brucellosis. However, bone marrow hypoplasia is a rare feature of the infection. An 11-year-old boy was admitted with fever, vomiting, and abdominal pain of 10 days' duration. On physical examination, pallor and high fever were detected in the absence of lymphadenopathy and hepatosplenomegaly. His hemoglobin was 8.6 g/dL, white blood cell count 1,100/mm(3), neutrophil count 500/mm(3), platelets 56,000/mm(3), and reticulocytes 0.1%. Hypocellular bone marrow was found by aspiration, and bone marrow biopsy revealed hypocellularity. The agglutination titer was greater than 1/640. Trimethoprim/sulfamethoxazole was prescribed. His fever subsided and pancytopenia subsequently improved. Pancytopenia associated with brucellosis is attributed to hypersplenism, hemophagocytosis, and granulomatous lesions of the bone marrow, which is usually hypercellular. Bone marrow hypoplasia is rarely reported and should be kept in mind in the etiology of aplastic anemia in a country where brucellosis is frequently encountered.

There is increased susceptibility to infections in β-thalassemia. Changes in T- and B-lymphocyte subsets and functions, defective chemotaxis, and phagocytosis of neutrophils and macrophages have been described in these patients. Regulatory T cells (Treg cells) play a crucial role in the maintenance of immunological self-tolerance. The FOXP3 gene is specifically expressed on Treg cells. Increased antigenic stimuli due to repeated blood transfusions might change the Treg cells and FOXP3 percentage in β-thalassemia. Immune functions of peripheral blood lymphocytes, percentage of Treg cells (defined as CD4(+)CD25(+)FoxP3(+)) were evaluated in 30 β-thalassemia major, 30 β-thalassemia trait, and 20 healthy children. Percentage of CD4(+)CD45RA(+) cells were increased in β-thalassemia trait compared to both β-thalassemia major and controls, whereas percentage of CD4(+)CD45RO(+) cells were higher in β-thalassemia major and trait patient compared to controls. Percentages of CD4(+)CD25(bright) and CD4(+)CD25(+)FoxP3(+) Treg cells were increased only in β-thalassemia major patients compared to controls (P = .001 and P = .0001, respectively). T lymphocytes express activated phenotype both in β-thalassemia major and trait patients. However, only in β-thalassemia major patients who were exposed to chronic antigenic stimulus as a result of repeated blood transfusions was an increase observed in Treg cells, which might suppress immune activation status.

BACKGROUND AND OBJECTIVES:Hepatitis B is a disease that is preventable with vaccination. Antibody levels after vaccination may be affected by suppression of the immune system due to cancer therapy. Children with cancer have a high risk of hepatitis B virus (HBV) infection. We aimed to assess the pretreatment immunization status against HBV infection and the rate of continuity of immunization after therapy in children with cancer.DESIGN AND SETTING:Retrospective case review of patients treated from 2004 to 2008.PATIENTS AND METHODS:We reviewed the medical records of patients treated in the departments of pediatric hematology and oncology and collected data on immunization history and hepatitis B serology. Anti-HBs antibody titers were compared before and after treatment.RESULTS:This study included 159 (99 males, 60 females) children who had a serologic examination. Antineoplastic therapy had been given for acute leukemia (n=66), non-Hodgkin lymphoma (n=27), Hodgkin lymphoma (n=20), and solid tumors (n=46). Fifty-one patients had not been immunized against HBV prior to the therapy; HBV serology was negative in 49 of these patients and HBsAg was positive in 2 patients. Anti-HBs antibody positivity was present in 99 of 108 patients with an immunization history, whereas no vaccination response was present in 9 patients. The titer of anti-HBs antibody was decreased below the protection level in 33 (33%) patients with positive anti-HBs antibody, whereas the protection level was found to be maintained in 66 (67%) patients. The most significant decrease (63.6%) was observed in leukemia patients. Posttreatment HBsAg and HBV DNA positivity was detected in two of the patients with negative pretreatment serology, whereas no HBV infection developed in the group with positive anti-HBs antibody.CONCLUSIONS:This study demonstrated the importance of routine childhood vaccination in reducing the risk of HBV infection in patients with cancer.

The demonstration of antiplatelet antibodies (PAIgG, PAIgM) and decreased detection of platelet surface antigens (CD41, CD61, CD42b) in children with immune thrombocytopenic purpura (ITP) have a diagnostic role. This study was conducted to determine whether these parameters differed in acute and chronic ITP. Chronic ITP was defined as thrombocytopenia persisting for more than 6 months from the onset of illness. A total of 80 subjects were divided into three groups: group 1 included 39 patients with acute ITP; group 2 included 31 patients with chronic ITP, and group 3 included 10 healthy children. At diagnosis, blood samples were obtained for platelet count, mean platelet volume, plateletcrit and platelet distribution width along with platelet surface antigens and antiplatelet immunoglobulins. We found that platelet surface antigens were significantly decreased in both acute and chronic ITP when compared to the control group (p = 0.001). In contrast, PAIgG was increased in acute and chronic ITP patients compared to the control group. PAIgM was significantly higher in acute ITP. We conclude that decreased platelet surface antigens and increased antiplatelet antibodies are observed in both acute and chronic ITP. In patients with chronic progress, a relatively lower level of PAIgM can be identified.