CHARACTERIZATION OF AN EOSINOPHILIC LEUKEMIA-CELL DIFFERENTIATION FACTOR (ELDF) PRODUCED BY A HUMAN T-CELL LEUKEMIA-CELL LINE, HIL-3

An adult T cell leukemia cell line, HIL-3, constitutively secretes a f actor which induces the phenotypical and functional eosinophilic diffe rentiation of a human eosinophilic leukemia cell line, EoL-1. Biochemi cal characteristics of the factor, termed eosinophilic leukemia cell d ifferentiation factor (ELDF), were examined. ELDF was precipitated by 35 to 65% saturated ammonium sulfate from the culture supernatants of HIL-3 cells (HIL-3 sup). ELDF was eluted in a peak corresponding to a molecular weight of 30 to 40 kd by gel filtration. Isoelectric focusin g in the Rotofor showed that ELDF had isoelectric points of 5 to 6. EL DF was trypsin-sensitive and stable to heat treatment at 65 degrees C for 30 minutes but labile at 80 degrees C or pH lower than 3. Half of the activity adhered to lentil-lectin but not to Con-A, indicating tha t a part of ELDF is glycoprotein with an N-linked carbohydrate moiety, which did not seem to be essential for ELDF activity. The biochemical characteristics of ELDF and blocking experiments using cytokine-speci fic neutralizing antibodies suggest that ELDF is different from gamma- interferon (IFN-gamma), tumor necrosis factor-alpha (TNF-alpha), granu locyte-macrophage colony-stimulating factor (GMCSF), interleukin-5 (IL -5) and interleukin-2 (IL-2), which may exist in HIL-3 sup, and that E LDF may be a previously unrecognized leukemia differentiation factor.