AFFINITY AND KINETICS OF THE INTERACTIONS BETWEEN AN ALPHA-BETA-T-CELL RECEPTOR AND ITS SUPERANTIGEN AND CLASS II-MHC PEPTIDE LIGANDS/

Immune activation is mediated by a specific interaction between the T- cell receptor (TCR) and an antigenic peptide bound to the major histoc ompatibility complex (MHC). T-cell activation can also be stimulated b y superantigens which bind to germline-encoded variable domain sequenc es of certain TCR beta-chains. We have used a surface plasmon resonanc e biosensor to characterize the molecular interactions between a class II-restricted alpha beta TCR and its superantigen and MHC/peptide lig ands. The extracellular domains of the murine D10 TCR (V alpha 2, V be ta 8.2) were expressed in insect cells and secreted as a disulfide-lin ked heterodimer. In the absence of MHC class II, purified soluble D10 TCR bound to Staphylococcus aureus enterotoxin C2 with an association rate of 1.69 +/- 0.12 x 10(4) M-1 sec(-1) and a dissociation rate of 1 .9 +/- 0.47 x 10(-2) sec(-1), giving a dissociation constant of 1.1 mu M. Binding of the TCR to S. aureus enterotoxin B was barely detectabl e and could not be measured accurately due to the rapid dissociation r ate. Soluble D10 TCR also bound to a soluble murine MKC class II I-A(k ) molecule containing a fused antigenic conalbumin peptide and complem entary leucine zipper sequences to facilitate efficient chain pairing. The purified I-A(k) chimera specifically stimulated proliferation of the D10 T-cell clone, and bound to immobilized soluble D10 TCR with an association rate of 1.07 +/- 0.19 x 10(4) M-1 sec(-1) and a dissociat ion rate of 2.2 +/- 0.65 x 10(-2) sec(-1), giving a dissociation const ant of 2.1 mu M. (C) 1997 Elsevier Science Ltd.