IL-2, IL-15, and EPO activate ERK2 in CTLL-EPO-R cells. CTLL-EPO-R cells were depleted of cytokine for 8 hours in RPMI-1 mg/mL BSA. Stimulations were conducted with no added cytokine (lane 1), 50 U of murine IL-2 per milliliter (lane 2), 100 ng of murine IL-4 per milliliter (lane 3), or 100 ng of simian IL-15 per milliliter (lane 4) or 50 U of human EPO per mL (lane 5). After cell lysis, an immunoprecipitation was performed using an anti-ERK2 antibody, followed by an in vitro kinase reaction using myelin basic protein (MBP) as an exogenous substrate. Samples were resolved by SDS-PAGE, transferred to nitrocellulose and then exposed to film.