不同等位基因E7/HLA-DR四聚体结合的结核患者CD4＋T细胞CDR3区序列分析

Analysis of TCR CDR3 sequences of E7/HLA-DR tetramers-bound CD4＋ T cells from tuberculosis patients by using tetramers constructed with different HLA-DRB1 alleles

目的 探讨机体抗结核免疫过程中CD4＋T细胞TCR与多肽/MHC之间的识别和结合规律.方法 从9例结核患者胸水中用等位基因不同的结核多肽E7/HLA-DR四聚体磁珠分选出E7结合阳性CD4＋T细胞,提取其RNA逆转录成cDNA作为模板扩增TCRα链和β链CDR3区核酸片段,并比较其长度和序列特征.结果 等位基因不同的E7/HLA-DR四聚体能够识别同一患者CDR3区序列相同或结构功能相似的CD4＋T细胞克隆.结论 结核患者体内CD4＋T细胞识别和结合抗原多肽时有一定的HLA-DR限制性,但是主要以多肽特异性为主,这为进一步探讨机体抗结核免疫中CD4＋T细胞和MHC之间的抗原提呈机制提供了数据.

Objective To investigate the recognition and binding mechanism between TCR of CD4＋ T cells and peptide/MHC （ major histocompatibility complex） in immune responses against Mycobacte-rium tuberculosis （MTB）. Methods Nine patients with tuberculosis （TB） were recruited in the present study. Peptide E7-bound CD4＋T cells were sorted by using E7/HLA-DR tetramers constructed with different HLA-DRB1 alleles from pleural fluid （ PLF） of TB patients. Total RNA was extracted and reversely tran-scribed into cDNA, which was used as the template to amplify complementarity determining region 3 （CDR3） fragments of T cell receptor （TCR） α and β chains. Amino acid sequences, spectratypes and lengths of the amplified CDR3 fragments were analyzed. Results The CDR3 amino acid sequences of E7-bound CD4＋ T cells were identical completely or partially in a single individual. E7/HLA-DR tetramers with different HLA-DRB1 alleles were capable of recognizing and binding CDR3 fragments with identical sequence or similar structure and function in one single individual. Conclusion The TCRαandβchains CDR3 line-age of CD4＋ T cells of TB patients apparently drifts, and the predominant CDR3 sequences of TCRαandβchains that recognize MTB antigen exhibit peptide specificity with some certain HLA-DR restriction. This study illustrates the possible causes and mechanisms of peptide-specific CD4＋T cells related antigen presen-tation against MTB.