| Objective:Idiopathic thrombocytopenic purpura (ITP) is one of the clinical syndromes that have unknown etiology.Because the immune system increases the destruction of platelets,ITP is also known as immune thrombocytopenic purpura .For a long time,the researches about the ITP's pathogenesis were mainly concentrated in the humoral immunity, that is,the combination of anti-platelet antibody and platelet surface target antigen results in platelet destruction in this autoimmune diseases. However, in recent years,people have found that cell-mediated immunity involved in the pathogenesis of ITP also play an important role,some studies have shown that activated T lymphocytes can be found in acute or chronic ITP patients.There are two signals (dual-signal) induct the T lymphocyte activation, proliferation, and differentiation to effective cells. The first signal is provided by the combination of antigen and T cell receptor;the second signal is provided by the binding of co-stimulatory molecules at APC surface and T cell surface receptor.Cytotoxic T lymphocyte-associated antigen -4 (CTLA-4) is the negative regulatory factor of T cell activation, the combination of B7 molecules at APC cell surface and CTLA-4 can inhibit the T cell proliferation, activation, induction of T cell tolerance. Reserch men have found that human CTLA-4 gene locates in chromosome 2q33,constituted by four exons and three introns.According to recent reserches, CTLA-4 gene has a number of sites which have polymorphism. The expression and function of CTLA-4 molecule maybe affected by gene polymorphism, abnormal CTLA-4 function and (or) expression may cause the occurrence and development of autoimmune diseases.For the past few years, researches about the relativity of CTLA-4 gene polymorphism and autoimmune diseases have made considerable progress,one of the most hot studies is the polymorphism about exon 1 A49G,but the association of CTLA-4 gene A49G polymorphism and ITP in Han Chinese population has not been confirmed.Now the CTLA-4 gene A49G signal peptide polymorphism of ITP patients and normal population who live around ShiJiazhuang in Hebei has been detected by our aboratory,and we hope that our work can prove its gene polymorphism in Chinese Northern Han population and its relationship with ITP.Methods:1 Experimental samples: genomic DNA was obtained randomly from 53 ITP patients and 126 healthy controls who belong to Han population in Hebei.2 Experimental group: all patients were divided into ITP groups and healthy control group to study the different genotype polymorphism , then all samples will be divided into two categories by gender to exclude the impact of gender,we study the differences between ITP patient group and healthy control group in the same sexual group.3 Experimental steps: extract genomic DNA from EDTA-treated blood,choose the forward primer and reverse primer,polymerase chain reaction - restriction fragment length polymorphism (PCR-RFLP) technology was used to treat samples.4 Judge the results: judge the genotype of the DNA locus based on the results of gel electrophoresis.5 Statistical Method: calculate genotype and allele frequencies according to the law of Hardy-Weinberg balance, then all functional data between groups are compared with theχ2 test by SPSS13.0 software, all tests were 2-tailed ,with ststistical significance set at P<0.05.Results:1 There are no statistical differences between ITP patients group and the normal control on the A/A, A/G, G/G genotype distribution and allele frequency of CTLA-4 exon 1 +49 in Hebei Han population (P> 0.05).2 After excluding the gender difference, we find that,in female,there is a significant statistical difference between ITP patients group and the normal control on the A/A, A/G, G/G genotype distribution and allele frequency of CTLA-4 exon 1 +49 (P <0.05), the A/G heterozygous genotype frequency of ITP patients group significantly higher than the healthy control (P<0.05); when compared the A,G allele frequency of two groups above,no significant difference can be foud(P> 0.05).In male,we see that there is no statistical significance between ITP patients group and the normal control on genotype distribution and allele frequency in Hebei Han population (P> 0.05).Conclusion: there is no significant correlation between CTLA-4 gene exon 1 +49 A/G signal peptide polymorphism and the susceptibility to ITP in Hebei Han population.In the female population, individual who has A/G heterozygous located in the CTLA-4 exon 1 +49 site have a higher susceptibility to ITP.
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