Adult T cell leukemia associated with eosinophilia: analysis of eosinophil-stimulating factors produced by leukemic cells.

The mechanism of eosinophilia in a patient with adult T cell leukemia (ATL) was investigated. A 61-year-old woman with ATL presented marked eosinophilia. No parasite infections or allergic diseases were found in this patient. The number of eosinophils fluctuated in parallel with that of ATL cells during her clinical course. The patient's serum and the culture supernatant of ATL cells showed eosinophil colony-stimulating activity. Northern blot analysis of granulocyte-macrophage colony-stimulating factor (GM-CSF), interleukin-3 (IL-3), and interleukin-5 (IL-5), which are known eosinophil CSFs, showed that only GM-CSF but not IL-3 or IL-5 was expressed in freshly separated and cultured ATL cells. Since neutrophil and monocyte numbers did not increase, it is suggested that GM-CSF and unknown cytokines other than IL-3 and IL-5 produced by ATL cells synergistically stimulated eosinophil precursors in the present case.