Production of an eosinophil chemotactic lymphokine by a monocyte-derived factor from patients with hypereosinophilia

Peripheral OKT4-positive T lymphocytes from patients with hypereosinophilia spontaneously and selectively produced an eosinophil chemotactic factor (ECF) with chemokinetic activity. The molecular weight of the ECF was about 45,000 to 70,000. A possible mechanism of its spontaneous production by T lymphocytes was analyzed. Culture supernatants of blood monocytes from the patients showed little or no ECF activity, but they had a potency to induce the ECF production from T lymphocytes from normal donors when the cells were stimulated by the supernatants, which suggests that a monocyte-derived soluble factor (MDF) stimulated T lymphocytes to produce an ECF resembling this spontaneously produced ECF from the patients. MDF seemed to be a synthesized protein by the cells. Gel filtration indicated that molecular weight of MDF ranged between 70,000 and 100,000. MDF activity was stable at 56 degrees C for 30 min but more, supernatants of stimulated monocytes by lipopolysaccharide or silica particles failed to show ECF-producing activity, whereas they showed evident lymphocyte-activation activity. Neither recombinant IL-1 nor IL-2 had ECF and ECF-producing activity. From the present experiments, it was suggested that MDF was at least partly involved in the induction of ECF production by OKT4-positive T lymphocytes in patients with hypereosinophilia.