IRAK1 and acute lymphoblastic leukemia: Of note, the IL-1β-induced IRAK1 increased phosphorylation was specifically observed in cell lines harboring basal IRAK1 phosphorylation (Jurkat and ALL-SIL T-cell lines) but not in HPB-ALL and DND-41, which express IRAK1 proteins without basal phosphorylation (Figure 2C right panel).