MURINE T-LYMPHOCYTE PROLIFERATION INDUCED BY INTERLEUKIN-2 CORRELATES WITH A TRANSIENT INCREASE IN P56(LCK) KINASE-ACTIVITY AND THE TYROSINE PHOSPHORYLATION OF A 97-KDA PROTEIN

The addition of recombinant interleukin 2 (rIL-2) to anti-CD3-activated murine G0 phase T cells results in an increased level of tyrosine phosphorylation of a single 97-kDa protein. The degree of tyrosine phosphorylation paralleled the amount of rIL-2 added and correlated with the extent of DNA synthesis. IL-2 treatment resulted in a transient increase in p56lck kinase activity without detectable modification of its level of tyrosine phosphorylation and gel mobility. When G0 T cells were activated by phorbol dibutyrate in the absence of IL-2, the high-affinity IL-2 receptor (IL-2R) expressed failed to induce a proliferative signal, and neither the tyrosine phosphorylation of the 97-kDa protein nor the transient increase in p56lck kinase activity was detected. Northern analysis of the total RNA extracted from these cells showed the accumulation of IL-2R alpha chain-specific mRNA but neither c-myc nor cdc2 mRNA was expressed. The addition of 100 nM rIL-2 to T cells activated by phorbol dibutyrate was able to induce a proliferative response, and under these conditions tyrosine phosphorylation of the 97-kDa protein, the transient increase in p56lck kinase activity, and specific mRNA for IL-2R alpha chain, c-myc, and cdc2 were detected. Unstimulated G0 T cells responded to 100 nM rIL-2 in the same manner as phorbol dibutyrate-activated cells. Irrespective of the signal-transducing structures involved, the IL-2-induced proliferative response closely correlates with an increase in p56lck kinase activity along with the tyrosine phophorylation of a 97-kDa protein.