Gleich, G.J.

Human peripheral blood eosinophils released eosinophil survival-enhancing activity when stimulated with the calcium ionophore, ionomycin. The release of activity was detected as early as 3 h after stimulation and was inhibited by an immunomodulating agent, cyclosporin A. The survival-enhancing activity was completely abolished by treatment with anti-interleukin 3 (IL-3) and anti-granulocyte/macrophage colony-stimulating factor (GM-CSF) monoclonal antibodies. Moreover, IL-3 and GM-CSF were measurable in ionomycin-stimulated eosinophil supernatants by immunoassay. Eosinophils produced approximately one-half as much IL-3 and one-fifth as much GM-CSF as ionomycin-stimulated mononuclear cells. Neutrophils also produced IL-3 and GM-CSF, but the amounts were less than those produced by eosinophils. These observations suggest a novel role for eosinophils in pathophysiology of allergic inflammation and host defense mechanisms.

Two of the four principal cationic proteins of the eosinophil granule, major basic protein (MBP) and eosinophil peroxidase (EPO), were shown to be platelet agonists. Both MBP and EPO evoked a dose-dependent nonlytic secretion of platelet 5-hydroxytryptamine in unstirred platelet suspensions even in the presence of 10 microM indomethacin. MBP also evoked secretion of platelet alpha granule and lysosome components. Secretion by MBP and EPO was inhibited by 1 microM PGE1, but the nature of the inhibition differed from that observed with thrombin. Thus, MBP and EPO can be classified as strong platelet agonists with a distinct mechanism of activation.

SUMMARY Eosinophils and eosinophil granule proteins may play an important role in the pathogenesis of asthma. BALF from 40 patients with symptomatic asthma were analysed for cytokine activity by the eosinophil survival assay. BALF from 15 patients showed increased survival activity. Survival activities in BALF from four of these patients were almost completely blocked by anti-IL-5 MoAb, and the remaining activities were blocked by anti-granulocyte-macrophage colony-stimulating factor (GM-CSF), anti-IL-3 antibody, or both. Surprisingly, BALF samples from the other 25 patients decreased eosinophil viabilities below the levels of medium control. The inhibitory factor in these BALF was of low molecular weight, was heat-stable, was largely overcome by excess exogenously added cytokines, and was positively correlated with the concentrations of lidocaine in the BALF. Lidocaine itself inhibited eosinophil survival at concentrations less than those present in the BALF. These findings indicate that lidocaine is an inhibitor of cytokines in the eosinophil survival assay, and they suggest the need for caution in analyses of BALF containing lidocaine or other local anaesthetics.