Cytotoxicity of IL-13 toxin and IL-4 toxin to CHO-K1 cells transfected with various chains of IL-13R.

CHO-K1 cells were transfected with various receptor chains and then IL-13 toxin– or IL-4 toxin–mediated cytotoxicity was determined by protein synthesis inhibition assay. CHO-K1 transfected with IL-13Rα2 (closed circles) or IL-4Rα (open circles) chains (A); cells were transfected with various combinations of receptor chains, control (closed circles), α1 α2 (open circles), α2 IL4Rα (closed diamonds), α1 IL4Rα (open diamonds), α1α2 IL4Rα (closed triangles) (B); cells transfected with increasing concentrations of DNA for IL-13Rα2 chain, 0 μg (closed circles), 1 μg (open circles), 2 μg (closed diamonds), 3 μg (open diamonds), 4 μg (closed triangles), 5 μg (open triangles), 6 μg (closed squares) (C); transfected with 6 μg cDNA of IL-13α2 chain and incubated with various concentrations of IL13-PE38QQR (closed circles) or IL4^38-37-PE38KDEL (open circles) (D); or transfected with control (open circles), IL4Rα (closed triangles), γ_c(open triangles), IL4Rαγ_c (closed squares). The results are represented as means ± SD of quadruplicate determinations, and the assay was repeated several times.