Fig. 6. Cell growth arrest by IL-9 is correlated with induction of p19/ink4d expression. A, BW5147 and BW-hIL9R cells were stimulated as described above with murine IL-9 and hIL-9, respectively. p19/ink4d expression was tested by Western blot with specific antibodies (Santa Cruz Biotechnology). B, cells expressing the indicated receptor were stimulated for 24 h with IL-9. RNA was extracted and analyzed by Northern blot with a specific 32P-labeled probe. Blots were quantified, and results were presented as a ratio between the signals obtained with the ink4d and the actin probes (C) in the absence (gray columns) or presence (black columns) of IL-9.