(A) Effect of Stat6 isoform expression on IL-4-induced mitogenesis in FDC-P2 cells. FDC-P2–Stat6 (light gray bar), FDC-P2–Stat6b (medium gray bar), FDC-P2–Stat6c (black bar), or control FDC-P2 (open bar) transfectants were treated with IL-4 at the indicated concentration. Each bar represents the average of three determinations ± SEM. Background uptake was typically less than 2000 cpm for each transfectant. (B) IL-4 induction of cell surface antigen expression on FDC-P2 or FDC-P2–Stat6 isoform transfectants. Cell surface staining of FDC-P2–Stat6, FDC-P2–Stat6b, FDC-P2–Stat6c, or control FDC-P2 transfectants was performed with FITC-conjugated anti-I-Ad or anti-CD16/32 after 72 h in the presence (solid line) or absence (dotted line) of IL-4. Fold induction (fluorescence intensity in the presence of IL-4/fluoresence intensity in the absence of IL-4) is presented in the upper right corner of each histogram.