We examined the eosinophil viability-enhancing activity (EVEA) of peripheral blood mononuclear cells (PBMNCs) obtained from 6 patients with mite-sensitive bronchial asthma (BA) and 9 normal control subjects. Mite concentrations of 1 microgram/ml and 10 micrograms/ml significantly increased EVEA in PBMNC culture supernatants from BA patients compared with PBMNCs from normal control subjects (76.1 +/- 11.0% at 10 micrograms/ml and 56.3 +/- 16.0% at 1 microgram/ml vs 20.6 +/- 12.6% at 10 micrograms/ml and 7.4 +/- 2.3% at 1 microgram/ml; p < 0.05). The level of IFN-gamma in PBMNC culture supernatants in BA patients was 2.3 +/- 0.9 IU/ml and in normal control subjects 0.7 +/- 0.3 IU/ml. A combination of mAbs (anti-IL-3, anti-IL-5 and anti-GM-CSF, with or without anti-IFN-gamma) neutralized the EVEA (p < 0.001, p < 0.001, respectively). Dexamethasone (10(-8) M to 10(-5) M), cyclosporin A (10(-7) M to 10(-5) M) and FK506 (10(-8) M to 10(-6) M) significantly inhibited EVEA in BA patients (p < 0.05 to p < 0.001). The release of eosinophil cationic protein (ECP) from eosinophils in the presence of mite-stimulated PBMNC culture supernatants was higher in patients with bronchial asthma (569 +/- 147 micrograms/l) than in normal control subjects (203 +/- 99 micrograms/l; p < 0.05).