| Aplastic anemia (AA) is characterized by failure of bone marrow hematopoiesis resulting in varying degrees of pancytopenia. Although its actual cause remains unknown. At present the pathogenesis of aplastic anemia has not been fully clarified. Possible mechanisms responsible for acquired AA include induced defects in heatopoietic stem cells, failure of the bone marrow microenvironment which impaired production or release of hematopoietic growth factors, and cellular or hurnoral immune suppression of the marrow. It has a high occurrence in children. Studies suggest that aplastic anemia was a significant heterogeneous disease. Immune-mediated mechanism has been considered the most important-in the pathogenesis of aplastic anemia. The introduction of immunosuppressive therapies such as antithymocye globulin (ATG), and cyclosporine A (CsA) in the treatment of aplastic anemia has improved the prognosis. Almost 70% patients recovered following immunosuppmssion therapy further confirmed the existence of aplastic anemia in patients with abnormal immune mechanisms. Most of aplastic anemia is a T-lymphocyte-mediated autoimmune disease. Further study T cells,especially abnormal activated T cells, were not only a useful marker to understand the pathegenesis of AA, but may have great implication on clinical application.Recent years, a variety of T-cell subsets that can inhibit T-cell responses has a role in the maintenance of auto-immune homeostasis. These cells have been named CD4+CD25+ regulatory T cells (Treg). The number of Treg reduction or loss of function often leads to autoimmune diseases, its secretion of transforming growth factor (TGF-β1) may play an important role. Some surface molecules have been reported to be responsible for the contact-mediated suppressive activity, but so far there are no specific markers on one mechanism being consistently involved. Transcription factor Foxp3 has been proved to be the most reliable and specific intracellular markers of Treg by now. Lately, several researches reveal that the expression of cell surface marker CD127 Was inversely correlated with the intracellular FoxP3 protein. So we can combinedly use CD4, CD25, CD 127 to detect the peripheral blood Treg in aplastic anemia patients.PurposeTo explore the role of them (Treg cell,Foxp3 gene,Serum TGF-β1) in the pathogenesis of aplastic anemia, accordingly, it may clarify the immune pathogenesis of aplastic anemia and provide valuable experimental evidence to look for new immunotherapy methods.Materials and methods30 AA patients were divided into two groups, the SAA group included 9 patients and the CAA group included 21 patients. Normal control group included 15 children. It is not statistically significant that the difference of age and sex in each group. To collect the peripheral blood prepares of children with AA before treatment, and the normal was collected from the healthy children. Applying flow cytometry to detect the expression of Treg. To get out total RNA, use RT-PCR and agarose gel electrophoresis techniques to semiquantitatively analyze Foxp3 mRNA expression. TGF-β1 was detected by ELISA technique. Use one-factor analysis of variance and pearson linear correlation to analysis the results with statistical software SPSS13.0 A p value of less than 0.05 was considered to indicate significance.Results1 Compared with normal controls, the percentage of peripheral blood CD4+,CD4+CD25+,CD4+CD25+CD127low T cells expression were decreased in patients with AA (P<0.05); SAA compared to patients with CAA, SAA group was lower than CAA group (P<0.05)2 The expression of FoxP3 mRNA decreased obviously in peripheral blood in SAA group (0.47±0.08)% compared with in the control group (0.71±0.12)% and the CAA group (0.68±0.14)%(P<0.05); The latter two was no significance (P> 0.05)3 Compared with normal controls (36.88±6.41) ng/ml, the expression of serum TGF-β1 were lower in SAA(10.72±3.35) ng/ml and CAA (18.26±5.05) ng/ml patients(P<0.05), and the expression of serum TGF-β1 were lower in SAA than CAA group(P<0.01).4 Correlation4.1 Aplastic anemia in children with CD4+ CD25+ CD127low T cell percentage and expression of TGF-β1 level were no significant correlation (r=0.136, P>0.05).4.2 The expression of CD4+CD25+CD127low T cell percentage in SAA patients had positive correlation with Foxp3 mRNA (r=0.76, P<0.05).Conclusions1 The low expression regulatory T cells and Foxp3 mRNA in AA patients may be involved in pathophysiology of AA, especially in patients with SAA, which is expected to assess the severity of AA.2 The expression of serum TGF-β1 were decreased in patients with AA, but were no significant correlation with Treg. It is suggestion TGF-β1 is not the only factor for Treg cells decline in aplastic anemia in children.
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