Expression of CD45 attenuates JAK/STAT activation. (A) Western blot analyses of JAK1, phosphorylated JAK1 (pY1022/1023), JAK2 and phosphorylated JAK2 (pY1007/1008) in EML cells expressing AML1-ETO, AE9a, and the MIP control. (B) Western blot analyses of STAT1, STAT3, STAT4, STAT5, and their phosphorylated forms (pY701, pY705, pY693, and pY694, respectively) in EML cells expressing AE9a and the MIP control. (C) Western blot analyses of JAK1, JAK2, STAT5, and their phosphorylated forms (pY1022/1023, pY1007/1008, and pY694, respectively) in EML-MigR1-AE9a cells expressing CD45 and the MIP control. Phosphorylated JAK2 was detected after JAK2 immunoprecipitation. (D) Flow cytometric analyses of phosphorylated STAT3 (pY705; left panel) and STAT5 (pY694; right panel) in the AEtr leukemia cell line expressing the full-length CD45.2 (CD45 FL) or a C-terminally truncated CD45.2 lacking the phosphatase domains (CD45 ΔC). The CD45.2⁺ cells were gated for analysis.