JAK2 and Chronic Eosinophilic Leukemia, Not Otherwise Specified: It is rational to consider that JAK2 may be the vital downstream kinase activated by F/P converged with IL-5-stimulated intracellular signals in CEL cells [37], and that excessive phosphorylation of JAK2 may promote higher levels of eosinophil infiltration and activation in CEL by activating signal cascades that are different from those in normal eosinophil biological function.