已有证据显示宿主CD4+ T细胞反应在幽门螺杆菌（H.pylori）感染中发挥着重要作用。免疫优势应答是抗细菌感染免疫的一个主要特征，但在抗H.pylori感染中CD4+ T细胞免疫优势应答还没被完全阐述。本课题组及其他研究小组已证实Lpp20是H.pylori的一个主要保护性抗原， 前期我们以BALB/c小鼠为模型，鉴定了Lpp20的H-2d限制性CD4+ T细胞表位。 考虑到小鼠和人MHC的差异及H-2d限制性表位不适用于人疫苗的设计，本课题拟以H.pylori感染者为对象，分离其外周血单个核细胞中特异性T细胞并体外扩增，利用重叠肽方法，对Lpp20中激发CD4+ T细胞应答的免疫优势表位进行筛选，并分析其HLA限制性，从而进一步评价Lpp20特异性CD4+T细胞反应与不同胃炎和胃溃疡的相关性，此研究将有助于全面理解H. pylori感染及宿主免疫防御机制并为研制新的表位疫苗提供基础。

Previous investigations have demonstrated that CD4+ T cells play a crucial role in pathogenesis of Helicobacter pylori (H.pylori) infection and immunological defense and CD4+ T cell epitopes exert a key function in T cell activation. Immunodominant response is an important feature of anti-bacterial cellular response, but it is not well elucidated in the immune response against H.pylori infection. Our team and other research groups have proved that Lpp20 is one of major protective antigens of H.pylori, which induce immune responses after H.pylori invades host. Base on BALB/c mice model, our previous study has identified two H-2d restricted CD4+ T cell epitopes on Lpp20 which predominantly induced Th1 type cell response to mainly secret IFN-γ. Taking into consideration the fact that MHC restriction is different between human and mice and H-2d restricted epitopes are not feasible to the design of human vaccine, we will target H.pylori-infected patients, isolate and expand Lpp20 specific T cells from peripheral blood monocytic cell (PBMC) of H.pylori patients, identify immunodomiant epitopes on Lpp20 using overlapping technology, analyze HLA restriction and access its correlation with various gastritis (atrophic gastritis, superficial gastritis, antral gastritis, fulfill stomach gastritis) and ulcer(duodenal ulcer, gastric ulcer). This study will provide insight into understanding H.pylori pathogenesis and host defense mechanism, and facilitate the development of effective epitope vaccine.