SECRETION OF DISULFIDE-LINKED HUMAN T-CELL RECEPTOR-GAMMA-DELTA HETERODIMERS

The availability of soluble forms of T-cell antigen receptors (sTCR) should be of great use in the detailed characterization of their interactions with ligands, for the generation of anti-TCR monoclonal antibodies (mAb), and for the eventual determination of their three-dimensional structures by x-ray crystallography. Here, we show that efficient secretion of nonchimeric disulfide-linked human gammadelta TCR could be achieved by simply introducing translational termination codons upstream from the sequences encoding TCR chain transmembrane regions. This recombinant protein appeared to be correctly folded, as judged by its reactivity with a panel of anti-gamma and anti-delta mAbs, and proved to be a powerful immunogen, allowing generation of mAb that are able to recognize both soluble- and membrane-bound gammadelta TCR. While variable and constant domains of gammadelta sTCR seem to be folded into compact conformations, the extreme sensitivity of its interchain disulfide bridge to digestion with papain suggests that sTCR C-terminal portions are in a more extended configuration than the corresponding region in immunoglobulins. Finally, the gammadelta heterodimer remains stable even after removal of the interchain disulfide link, suggesting the existence of strong noncovalent forces holding the two chains together.