T cell receptor-extracellular constant regions as hetero-cross-linkers for immunoglobulin variable regions.

The T cell receptor alpha and beta chains are covalently linked via a disulfide bond in their extracellular constant regions. To use these domains as specific hetero-cross-linkers of two different polypeptides, we created genetic constructs encoding a chimeric antibody Fab fragment in which mouse immunoglobulin constant regions from a phosphorylcholine-specific antibody were substituted for human alpha beta-T cell receptor (TCR) extracellular constant regions (for solubilization, the transmembrane- and cytoplasmic-regions of the receptor were deleted). These constructs, i.e., chimeric heavy (VHC beta C kappa) and light (VLC alpha) chains, were cotransfected into murine SP2/0 myeloma cells for expression. Cells transfected with the genes expressed mRNAs for chimeric heavy and light chains. Without CD3 molecules, the two chimeric chains specifically associated via a disulfide bond to form a chimeric Fab fragment in the cells. These data indicate that the TCR C alpha- and C beta-regions might be used as potent specific hetero-cross-linkers for protein engineering.