IL-6–induced growth inhibition of 1A9-M cells. (A) 1A9-M cells were cultured with or without 20 ng/mL IL-6 for the indicated time periods. (B) 1A9-M cells were cultured with various concentrations of IL-6 for 3 days. The results of hemocytometer counts are shown as the mean ± SD of triplicate cultures.