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

Objective To investigate the recognition and binding mechanism between TCR of CD4+ T cells and peptide/MHC (major histocompatibility complex) in immune responses against Mycobacterium 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 transcribed 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 TCR α and β chains CDR3 lineage of CD4+ T cells of TB patients apparently drifts, and the predominant CDR3 sequences of TCR α and β chains 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 presentation against MTB. Key words: Tuberculosis; E7; HLA-DR tetramer; CDR3; CD4+ T cell