T cell antagonism is functionally uncoupled from the 21- and 23-kDa tyrosine-phosphorylated TCR ζ subunits

The functional effects of altered peptide ligands on T cells is proposed to involve differential intracellular signaling mediated by the 21- and 23-kDa tyrosine-phosphorylated derivatives of the TCR ζ subunit (p21 and p23). To understand the functional contribution of p21 and p23 to T cell development and T cell antagonism, we generated selected TCR ζ transgenic mice maintained on the P14 αβ TCR transgenic line such that p23 or both p21 and p23 were selectively eliminated. Importantly, one line (YF1,2) retains the constitutively tyrosine-phosphorylated p21 in the complete absence of inducible p23. We determined that T cell development was uncoupled from p21 and/or p23. Using a series of agonist, weak agonist, and antagonist peptides, we analyzed the role of each of the phosphorylated forms of TCR ζ on T cell activation and antagonism. In this study, we report that the proliferative responses of αβ P14 T cells to agonist peptides and the inhibition of proliferation resulting from antagonist peptide treatments was functionally uncoupled from p21 and/or p23. These results suggest that the mechanism of T cell antagonism is independent of the two phosphorylated TCR ζ derivatives.