Activation of human T lymphocytes via the CD2 antigen results in tyrosine phosphorylation of T cell antigen receptor ζ-chains

The phosphorylation of the invariant chains associated with the human TCR has been investigated after the stimulation of T lymphocytes with CD2 mAb T11₂ and T11₃, PHA, or phorbol 12,13-dibutyrate. As described previously, stimulation of T cells with either CD2 mAb or phorbol 12,13-dibutyrate resulted in the phosphorylation of the CD3 γ-chain. The combination of T11₂ and T11₃ mAb also induced phosphorylation of the TCR ζ-chain. The phosphorylated ζ-polypeptide of CD2-activated cells was immunoprecipitated with antiphosphotyrosine antibodies and migrated to a 21- to 23-kDa position during SDS/PAGE. These results indicate that stimulation of human T cells via the CD2 Ag with the T11₂ and T11₃ mAb activates not only protein kinase C but also tyrosine kinase(s), resulting in the phosphorylation of the CD3 γ-chain and the tyrosine phosphorylation of the ζ-chain, respectively.