中文摘要：

目的：探讨B7-H3分子2种异构体在不同物种中的分布及其演化模式以辅助研究B7-H3分子的生物学功能。方法：通过生物信息学方法从各类数据库中搜索脊椎动物各物种的B7-H3分子序列,分析其结构域的数量及剪切形式预测异构体的分布;获取代表性物种的组织抽提RNA,PCR验证预测结果;计算各物种B7-H3分子中V1C1和V2C2的dN和dS比。结果：获取了38个物种的B7-H3序列,其中豚鼠、家犬、非洲象、牛、熊猫、蝙蝠及高级灵长类动物如黑猩猩、大猩猩、猴等物种中存在2种剪切体;RT-PCR方法证实了2种剪切体的表达。各物种V1C1与V2C2序列的非同义突变（dN）大于同义突变（dS）值。结论：B7-H3分子最早以2IgB7-H3形式存在于硬骨鱼动物中,在高级哺乳动物中出现了2种异构体;且在自然界压力选择下发生了净化选择,并未产生新的生物学功能。

英文摘要：

Objective：To discuss the distribution of B7-H3 two isoforms in various invertebrates and its evolution model to help researching the function of B7-H3.Methods：The various B7-H3 sequences were searched in various databases through bioinformatics methods and analyzed the number of structure domains and the splicing forms to deduce the distribution of B7-H3 in various species.PCR analysis after acquiring the RNA from representative species were performed to verified the prediction.The calculation of ration of dN and dS were also done.Results：We acquired thirty-eight B7-H3 sequences and 4IgB7-H3 was also presented in guniea pigs,dogs,african elephants,panda,bat and higher primate animals,which were verified by PCR analysis.The dN valule of V1C1 and V2C2 sequences was greater than dS value.Conclusion：B7-H3 was earliest expressed in teleost with the form of 2IgB7-H3 and the function of B7-H3 was consistent in evolution.