Recovery of JAK-1 in anti-phosphotyrosine immunoprecipitates from IL-6–dependent and –independent cell lines.

IL-6–dependent cells (7TD1 and B9) were cultured continuously in IL-6–containing medium or starved from IL-6 for 48 hours and restimulated with 100 U/mL IL-6 for 20 minutes. IL-6–independent cells (SP2/0, 7TD1Ind, and B9Ind) were cultured continuously in medium without IL-6 or stimulated with 100 U/mL IL-6 for 15 minutes. Cell lysates were prepared and subjected to immunoprecipitation with anti-phosphotyrosine antibodies, resolved by 8% SDS-PAGE, and immunoblotted with anti-JAK-1 antibodies.