Expression And Clinical Significance Of CD₄,CD₂₈,sFas And SFasL In The Peripheral Blood Of Children With Idiopathic Thrombocytopenic Purpura

Idiopathic thrombocytopenic purpura (ITP) is one of the most common acquired bleeding disorder in children. Its main clinic characteristics are spontaneous hemorrhage of skin and mucosa, plate-reduction, normal or increased megacaryocytes count in bone marrow. It could be classified into acute (six months or less in duration, AITP) and chronic (more than six months, CITP) by course. In the majority of children, ITP is an acute, self-limiting disorder with complete resolution of illness occurring within 6 months. However, 20% to 30% of children with ITP develop a chronic form of the disease defined as persistence of thrombocytopenia beyond 6 months, and a few of them will become to the refractory ITP (RITP) because of bad therapeutic effect.The pathogenesy of this disease has not been understood. But now it's known as an autoimmune disease. The causes of the decreasing platelets count are that the children with ITP who have autoimmunity disorder produce antiplatelet antibody and a great quantity of platelets are phagocytized by monocaryon-macrophage system. The production of autoantibody is dependent on the Th cells. Recent studys discover that the disease's development is related to the activated lymphocytosis, deficient apoptosis in peripheral blood and so on .CD4 cell is a significant subset of T lymphocyte, which includes Th cell (assistant T lympholeukocyte) and Ts (delayed hypersensitive reactive T cell). CD₄⁺ Th cell can be classified as Th1 and Th2; the former mainly secretes IL-2, TFN-γand so on, which regulate the cell-immunity, and the latter mainly seretes IL-4 and IL-10, which modulate the humoral-immunity. At present, the studys indicated that the balance of Th1/Th2 plays an important role in the development of autoimmune diseases. However, in ITP it's unknown which one prevail, and this should be investigated further.CD₂₈, a transmembrane glycoprotein, is the most significiant costimulatory signal to active T cell. The dormant T cell can be actived and proliferated effectively with double-signal-ways. One is antigen interaction of TCR and APC, the other is the costimulatory signal from T cell accessory molecule interacting with APC ligand. If there is only antigen interaction of TCR and APC,without costimulatory signal , it could lead to activation induced cell death (AICD) of T cell. The intracellular signal priming from CD₂₈/B₇ can protect T cell from apoptosis, because of evading T cell from AICD, making the expression of anti-apoptosis gene bcl-XL increase, and down-regulating apoptosis gene Fas.Apoptosis is a cellular autonomy death procedure controlled by gene. Recent studies manifested that Fas/FasL played a key role in apoptosis. Fas is I-type membrane protein, belonging to the family of tumor necrosis factor (TNF) receptor; and Fas ligand is II -type membrane protein, belonging to the family of tumor necrosis factor (TNF). sFas (solubility type of Fas) is from proteinase binding Fas or mRNA of Fas's var. translating; sFasL (solubility type of FasL) is from metalloprotease lysis membrane conjuncting with FasL. sFas can regulate apoptosis by integrating FasL . The studies investigated that many patient with autoimmune diseases had peripheral blood lymphocyte dys-apoptosis. The aim of the study is to detect the expression of CD₄,CD₂₈,sFas and sFasL in acute and chronic idiopathic thrombocytopetic purpura and to explore their roles in the pathogenesy of children with ITP, and to search for differences between AITP and CITP in immune mechanism, and to support theory basis to practice high effectively and selectively immunoregulation treatment for ITP, especially for CITP.Materials and Methods1. SubjectWe choose 45 children with ITP of inpatient and outpatient of The First Affiliated Hospital of ZhengZhou University from January to August in 2006. There are 25 AITP and 20 CITP, whose age is from six months to thirteen years and the average is five point three years. The diagnosis is coincidence with the standard of the Chinese Pediatrics Hematology Conference. The control group is 20 children without hematological system diseases and immunity diseases, whose age is from three to eight years ,and the average is six point two years.2. MethodsWe detected the expression of CD₄⁺,CD₂₈⁺,CD₄⁺CD₂₈⁺ in children with ITP and control groups by flow cytometry, and choose six thousand cells in every sample and analyze these with CELLQUGST software; we used ELISA way detecting the levels of sFas and sFasL. All the data were manifested by mean±standard deviation ((x|-)±s,%), and analyzed by 13.0 software package. Measurement data were based on test criterion of a=0.05,and P<0.05 presents significance differences.Results1. The expression rates of CD₄⁺,CD₂₈⁺,CD₄⁺CD₂₈⁺ in peripheral blood are respectively 27.64±5.99, 35.19±10.52, 24.82±5.89 in AITP group; 24.48±4.35, 31.94±7.09, 22.55±4.00 in CITP group; 36.83±3.96, 52.58±9.38, 33.87±3.94 in control. In addition, the expression rates of CD₄⁺,CD₂₈⁺,CD₄⁺CD₂₈⁺ in AITP and CITP groups are significantly lower than in the control(P<0.05); there is no difference in AITP and CITP groups(P>0.05). 2. The levels of sFas and sFasL in peripheral blood are respectively 15.69±1.62, 0.73±0.10 in AITP group; 11.77±2.14, 0.49±0.12 in CITP group; 5.77±1.13, 0.31±0.02 in control. In addition, the levels of sFas and sFasL have signicant difference among AITP,CITP and control groups(P<0.05).3. Correlation analysis The levels of sFas and sFasL in peripheral blood have positive correlation in AITP and CITP groups (r=0.660, P<0.05); and there is no correlation between the expression of CD₂₈ and sFas(P>0.05).Conclusion1. There is cell dysimmunity in the pathogenesis of ITP in children.2. The CD₂₈ cositimulatory signal pathway participate the mobidity of ITP in children.3. Apoptosis system of sFas and sFasL are related to ITP in children, and they might play a more important role in AITP group.4. There will be great significiance for the type and prognosis in children with ITP by detectiing the levels of sFas and sFasL in peripheral blood .And they will give us theory basis to practice high effectively treatment for children with CITP, especially RITP.