gp130 phosphorylation in IL-6–dependent and –independent cell lines.

IL-6–dependent cells were cultured continuously in IL-6–containing medium or starved from IL-6 for 10 hours (T1165), 30 hours (T2027), or 48 hours (7TD1 and B9) and restimulated with IL-6 (500 U/mL) for 20 minutes. IL-6–independent cells were cultured continuously in medium without IL-6 and stimulated with IL-6 (100 U/mL) for the indicated times (SP2/0, MOPC315, and MOPC31C) or stimulated for 20 minutes with the indicated doses of IL-6 (B9Ind and 7TD1Ind). Anti-gp130 immunoprecipitates were resolved by 10% SDS-PAGE, and phosphorylation of gp130 was detected by immunoblotting with an anti-phosphotyrosine antibody. Blots were stripped and reprobed with anti-gp130 antibody.