Figure 2.

Proliferative responses of CTLL-2 cells expressing chimeric receptor chains derived from αγ and Jak3. (A) S phase entry assessed by incorporation of tritiated thymidine in response to human GM-CSF (10 ng/ml) or media alone plotted as a percentage of the response to human IL-2 (20 units/ml), which ranged from 3–6 × 10⁴ cpm. All cells also expressed an intact version of ββ, except those denoted αγPROX–J3 + ΔS, which expressed the deletion mutant ββ–ΔS. For each receptor combination, the responses of three independent CTLL-2 subclones are shown. Similar relative responses were observed over a range of GM-CSF concentrations from 0.1 to 100 ng/ml (data not shown). (B) Growth of a subclone of CTLL-2 cells coexpressing αγPROX–J3 and ββ and cultured with GM-CSF (100 ng/ml), IL-2 (100 units/ml), or media alone. Identical results were obtained with three other independent subclones. (C) Western blot analyses to detect nuclear expression of the proto-oncogene products p67^c-myc and p62^c-fos after stimulation with GM-CSF (GM; 100 ng/ml) or IL-2 (100 units/ml) for 1–4 h.