Constitutive activation of Stat3 in CTCL is Blk independent. Malignant T cells (MF2000) were incubated for different time intervals (hours) with LckI (10 μM), Jak3I (40 μg/mL), or vehicle (−). Subsequently, immunoprecipitated Blk (IP: Blk) and respective total cell lysates (Lysate) were analyzed by WB using antibodies against phosphotyrosine, Blk, pY-Stat3, Stat3, and Erk.