IL‐2‐dependent in vivo and in vitro tyrosine phosphorylation of IL‐2 receptor γ chain

Abstract
We previously reported a molecule, p64, which was tentatively named the γ chain, coprecipitable with the β chain of human interleukin‐2 receptor (IL‐2R). The present study demonstrated that the γ chain, as well as the β chain expressed on IL‐2‐responsive cells, is phosphorylated on tyrosine residues in an IL‐2‐dependent manner in vivo and in vitro. The in vivo tyrosine phosphorylation of both chains was similarly induced within 1 min after IL‐2 stimulation, and their in vitro tyrosine phosphorylation with the anti‐IL‐2Rβ antibody‐directed immunocomplex was also increased by treatment of cells with IL‐2. These results suggest that a tyrosine kinase is associated with the βγ subunit complex, of which activation by IL‐2 may result in transduction of intracellular signals.