STRUCTURE OF THE T-CELL RECEPTOR IN A TI-ALPHA-V-BETA-2,ALPHA-V-BETA-8-POSITIVE T-CELL LINE

The T cell receptor (TcR) is composed of at least six different polype ptide chains consisting of the clonotypic Ti heterodimer (Ti alpha bet a or Ti gamma delta) and the noncovalently associated CD3 chains (CD3 gamma delta epsilon zeta). The exact number of subunits constituting t he TcR is still not known; however, it has been suggested that each Tc R contains two Ti dimers. To gain insight into the structure of the Tc R we constructed a Ti alpha V beta 2, alpha V beta 8-positive T cell l ine which expressed the endogenous human TiV beta 8 and the transfecte d mouse TiV beta 2 both in association with the endogenous Ti alpha an d CD3 chains at the cell surface. Preclearing experiments with radioio dinated cell lysate prepared with digitonin lysis buffer demonstrated that depleting the lysate of Ti alpha V beta 8 by immunoprecipitation with anti-V beta 8 monoclonal antibody (mAb) did not reduce the amount of Ti alpha V beta 2 in the lysate, and likewise, depleting the lysat e of Ti alpha V beta 2 with anti-V beta 2 mAb did not reduce the amoun t of Ti alpha V beta 8. Comodulation experiments showed that V beta 8 and V beta 2 did not comodulate with each other. Furthermore, function al tests demonstrated that TcR containing V beta 8 and TcR containing V beta 2 mediated transmembrane activation signals independently of ea ch other. These data demonstrate that mouse V beta 2 and human V beta 8 were not expressed in the same TcR in agreement with a TcR model whe re each TcR contains only one Ti dimer.