Changes in arrangement and in conformation of molecular components of peripheral T-cell antigen receptor complex after ligand binding: analyses by co-precipitation profiles.

Amounts of co-precipitating CD3 components by anti-T-cell receptor (TCR)V beta or anti-CD4/8 monoclonal antibodies were compared between non-stimulated and stimulated splenic T cells. The amounts of co-precipitating CD3 delta, epsilon and gamma chains with TCR alpha beta and with CD4/8 were not significantly changed after TCR ligation. The apparent amount of CD3 zeta chain co-precipitated with TCR alpha beta increased up to threefold, while the actual amount of co-precipitating CD3 zeta with TCR alpha beta and the total amount of specifically precipitated CD3 zeta are not changed after cross linking of TCR. The apparent amount of CD3 zeta chain co-precipitated with CD4/8 also increased. Unlike co-precipitation with TCR alpha beta, the actual amount of CD3 zeta co-precipitated with CD4/8 increased significantly. This observation suggests a conformational change as well as the relocation of CD3 zeta molecules within the TCR complex after the signal delivery. After TCR ligation, CD3 zeta chains relocate to the vicinity of either CD4 or CD8 molecules. In addition, when cross linking and binding signals are compared, CD3 chains undergo two distinct phases of conformational change. The responses, while the later conformational change caused by the cross linking of TCR does not induce but enhances the proliferative response.