ABSTRACTAntigen-specific γδ T cells may play an important role in the immune response toMycobacterium tuberculosis. However, little is known about the characteristics of the length distribution of the δ2-chain complementarity determining region 3 (δ2 CDR3) of the γδ T-cell receptor (TCR) in patients with active pulmonary tuberculosis (TB) on a large scale. In addition,M. tuberculosis-activated γδ T cells potentially inhibit intracellular mycobacterial growth, but phosphoantigen-activated γδ T cells do not. Only a fewM. tuberculosis-related antigen peptides or proteins that are recognized by γδ TCR have been identified. Twenty-four healthy donors (HDs) and 27 TB patients were included in the present study. The gene-scanning technique found that the δ2 CDR3 length distribution patterns of γδ TCR in TB patients were perturbed, and each pattern included different predominant CDR3 sequences. The predominant δ2 CDR3 sequences of γδ TCRs, which originated from TB patients and HD γδ T cells that were stimulated byM. tuberculosisheat resistance antigen (Mtb-HAg), were used as probes to screen peptides recognized by γδ TCR using a phage display library. We identified four peptides that bound to the predominant δ2 CDR3 fragments and showed homology toM. tuberculosisgenes in a BLAST search. Notably, one peptide was related toM. tuberculosisH37Rv (QHIPKPP), and this fragment was confirmed as a ligand for the γδ TCR. Two fragments, Ag1 and Ag2, activated γδ T cells from HD or TB patients. In summary, the δ2 CDR3 lineage of TB patients apparently drifts, and the predominant δ2 CDR3 sequence that recognizesM. tuberculosismay exhibit specificity. The identifiedM. tuberculosis-related antigen peptides may be used as vaccines or adjuvants for protective immunity againstM. tuberculosis.
Loss of Receptor on Tuberculin-Reactive T-Cells Marks Active Pulmonary Tuberculosis