As expected immunoprecipitation of cell extracts with anti-PDGFRA antibody followed by immunoblotting with anti-phosphotyrosine (4G10), showed that phosphorylated F/P proteins were only detected in the 11 F/P(+) CEL patients (Figure 1A, D). This evidence concerns the gene PDGFRA and Chronic Eosinophilic Leukemia, Not Otherwise Specified.