IL5 and Chronic Eosinophilic Leukemia, Not Otherwise Specified: CEL has been initiated in mice by the combination of fusion protein FIP1L1-PDGFRα (F/P) expression and IL-5 overexpression [139], resulting in a less severe eosinophilia development in the absence of Atg5. Similar results were obtained in EoL-1 cells, a model of an established human CEL.