Antigen recognition properties of a Vγ1.3Vδ2-T-cell receptor from a rare variant of polymyositis

Abstract

Previously we partially characterized an autoreactive human Vγ1.3Vδ2-T-cell receptor (TCR) that had originally been identified in muscle of a patient with an unusual form of polymyositis. This TCR recognizes a muscle-associated auto-antigen in a CDR3-dependent, MHC non-restricted way. Here we show that this TCR also recognizes an antigen from Escherichia coli. Like the muscle-associated mammalian antigen, the bacterial antigen is recognized in a CDR3-dependent, but MHC-non-restricted way. Both antigens have strikingly similar molecular characteristics suggesting that their epitopes are at least very similar. The dissociation kinetics of the bacterial antigen-TCR complexes was investigated by surface plasmon resonance using soluble single-chain TCR molecules produced in COS-7 cells. The measured dissociation rate constant ( k off=5.7×10 −3 s −1) shows that the complexes dissociate more slowly than most previously described antigen/αβ-TCR complexes, but much faster than antibody/antigen pairs. These results (a) provide further insight into the molecular properties of this unusual TCR, and (b) should help in future attempts to identify the elusive target antigen(s).