Expression, Purification, and Crystallization of the Vγ9Vδ2 T-cell Receptor Recognizing Protein/Peptide Antigens.

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γδ T cells, especially Vγ9Vδ2 T cells, play an important role in mycobacterial infection. We have identified some Vγ9Vδ2 T cells that recognize protein/peptide antigens derived from mycobacteria, which may induce protective immune responses to mycobacterial infection. To clarify the structural basis of the molecular recognition mechanism, we tried many methods to express the Vγ9Vδ2 T-cell receptor (TCR). The Vγ9Vδ2 TCR was not expressed well in a prokaryotic expression system or a baculovirus expression system, even after extensive optimization. In a mammalian cell expression system, the Vγ9Vδ2 TCR was expressed in the form of a soluble heterodimer, which was suitable for crystal screening. Reduced-temperature cultivation (cold shock) increased the yield of the recombinant TCR. The recombinant purified TCR was used for crystal trials, and crystals that could be used for X-ray diffraction were obtained. Although we have not yet determined the crystal structure of the Vγ9Vδ2 TCR, we have established a procedure for Vγ9Vδ2 TCR expression and purification, which is useful for basic research and potentially for clinical application.