Spontaneous Production of Interleukin-5 and Its Heterogeneous Effect on Eosinophils in an Adult T-Cell Leukemia Patient

Abstract

We examined the functional heterogeneity of eosinophils from an adult T-cell leukemia (ATL) patient with eosinophilia. A 63-year-old man was admitted to our hospital because of lymphadenopathy. The leukocyte count was 10 400 /mm3, with 36.0% eosinophils and 3.0% abnormal lymphocytes. The diagnosis of ATL was based on the presence in serum of anti- human T-cell lymphotrophic virus-1 antibody and on histologic demonstration of ATL cells. The mononuclear cells spontaneously produced eosinophil-related cytokines (granulocyte-macrophage colony stimulating factor, 5600 pg/mL; interleukin (IL)-5, 375 pg/mL). Peripheral eosinophils were fractionated into normodense eosinophils (NE) and hypodense eosinophils (HE) by a Percoll density gradient method, and these cells were compared in terms of several heterogeneous functions. The NE were more chemotactically attracted to IL-5 than the HE. More apoptotic cells appeared among the NE than among the HE and this difference was correlated with the positive rate of Fas antigen on eosinophils. Survival of the HE was longer than that of the NE. Survival of the HE was prolonged by IL-5 stimulation, but survival of the NE was not. These data suggest that functionally heterogeneous eosinophils were present in this ATL patient with eosinophilia and that IL-5 enhanced this heterogeneity. The response of eosinophils to IL-5 may have contributed to the patho- genesis of eosinophilia in this patient.