Fig. 4.
Effects of hIL-3 (M) Rα activation.
(A) Cell surface expression. hIL-3 (M) Rα, hβc cell transfects were analyzed for expression of the extracellular domains of the (i) hIL-3 Rα and (ii) hβc by flow cytometry. Cells were sequentially incubated with anti–hIL-3 Rα antibody and fluorescein isothiocyanate (FITC)–conjugated antimouse secondary antibody. The solid gray histogram represents the cell autofluorescence obtained in the absence of antibody staining. Representative histograms are shown for labeling obtained in the presence of secondary antibody only (gray) and in the presence of both primary and secondary antibody (black). (B) Cell survival proliferation. Cells expressing wild-type hIL-3 Rα, hβc (░) or hIL-3 (M) Rα, hβc (▪) were cultured in hIL-3 (0-100 ng/mL). (i) Cell viability was assessed at 48 hours using trypan blue. The results are expressed as cell viability (percent rmIL-3 response) and are mean values ± SEM from at least 3 experiments. (ii) [3H]-thymidine incorporation was assessed after 16 hours in culture. The results are expressed as percentage of the response obtained with rmIL-3 (10 ng/mL). (C) Cell morphology. Cells expressing (i) wild-type hIL-3 Rα, hβc or (ii) hIL-3 (M) Rα, hβc were cultured in hIL-3 (1 ng/mL) for 7 days. Photomicrographs were prepared from May-Grünwald-Giemsa–stained cytospin preparations. Results are representative of 3 experiments. Bar is 10 μm.