H-2Db四聚体的制备及其在检测LCMV特异性CD8+ T细胞中的应用

MHC四聚体技术是研究抗原特异性淋巴细胞应答的关键技术之一。为研究H-2Db基因型(如C57BL/6)小鼠的特异性CD8+ T细胞免疫应答, 需要建立H-2Db四聚体制备技术平台。首先以RT-PCR方法克隆H-2Db重链基因的cDNA, 进而构建H-2Db胞外域与生物素化酶BirA底物肽(BSP)融合蛋白的表达载体, 并在大肠杆菌中获得表达。在LCMV GP33-41抗原肽(KAVYNFATC, KAV)和人β2-微球蛋白存在时, 通过稀释法复性获得H-2Db/KAV单体。该单体经生物素化并纯化后与PE-链亲和素按4: 1的比例混合, 即形成四聚体。通过流式细胞术检测经KAV肽免疫的C57BL/6小鼠体内的LCMV特异性CD8+ T细胞的频率, 结果表明在外周血、引流淋巴结和脾脏中均可检测到一定频率的LCMV特异性CD8+ T细胞, 其中以对外周血标本染色的效果最佳。成功建立了小鼠H-2Db四聚体制备技术平台, 为监测及分析基于H-2Db基因型小鼠的实验性免疫治疗创造了条件。

Preparation of H-2Db Tetramer and Its Application in Enumerating the CD8+ T Cells Specific for Lymphocytic Choriomeningitis Virus

Major histocompatibility complex (MHC) tetramer technology offers a powerful means to study specific T cell populations of interest. To investigate the immune response of H-2Db-restricted CD8+ T cells in immunotherapy, we prepared the H-2Db tetramer and verified its effectiveness in enumerating the CD8+ T cells specific for the lymphocytic choriomeningitis virus (LCMV). First, the cDNA encoding H-2Db heavy chain was cloned by RT-PCR from the spleen of a C57BL/6 mouse. The expression vector for H-2Db-BSP, i.e. the ectodomain of H-2Db fused to a BirA substrate peptide (BSP), was constructed and overexpressed in E. coli BL21(DE3). Then, the denatured H-2Db-BSP was refolded in the presence of human beta2-microglobulin as well as the GP33-41 peptide (KAVYNFATC, KAV) of LCMV. The biotinylated H-2Db/KAV molecules were purified, then bound to streptavidin-PE and tetramerized. Finally, the prepared H-2Db KAV tetramer reagent was verified by detecting the CD8+ T cells specific for HCMV in KAV peptide vaccinated C57BL/6 mouse, with a mouse receiving subcutaneous injection of only adjuvant as negative control. The results showed that the tetramer positive rates were 0.27%, 0.11%, and 0.24% within the CD8+ T cell populations in the peripheral blood, draining lymph nodes, and spleen of vaccinated mouse, respectively. There was only very low background staining (< or = 0.01%) of those samples from the control mouse. Beside, the best results were achieved in the staining of the peripheral blood sample. In conclusion, the established procedure of preparing H-2Db tetramer will facilitate the study of the immune responses of antigen-specific CD8+ T cells in the experimental immunotherapy on the mice with H-2Db allele background.