Treatment with anti-IL-6 but not anti-IL-1 blocks constitutive Stat3 phosphorylation and restores IL-6 inducibility.

(A) AML cells (patient 19) were cultured in 12-well plates and pretreated with either anti-IL-6 (1:1000) or left untreated. After 24 hours, cells were washed and were left unstimulated or were stimulated with 10 ng/mL IL-6 for 15 minutes. (B) AML cells (patients 18, 20) were cultured in 12-well plates and stimulated with 10 ng/mL IL-6 for several time periods as indicated. After 24 hours, cells were treated with anti-IL-6 (1:1000) as indicated for 15 or 60 minutes. Equal amounts of total cell lysates were subjected to SDS–PAGE, followed by Western blot analysis as described in A. (C) AML cells (patient 18) cultured in 12-well plates were either pretreated with anti-IL-1 (1:250) overnight or left untreated. After 24 hours, cells were washed and stimulated with 10 ng/mL IL-6 for 15 minutes as indicated. Equal amounts of total cell lysates were Western blotted as described in A.