Interleukin-5-induced granulocyte activation in atopic patients

The effect of recombinant human and murine interleukin-5 (IL-5) on granulocytes was investigated in patients with atopic dermatitis (AD) and allergic rhinitis and compared with those from patients with plaque psoriasis and normal non-atopic controls. Granulocyte activation was measured as lucigenin-dependent chemiluminescence (CL) and release of eosinophil cationic protein (ECP) as well as by scanning- and transmission-electron microscopy (EM) and the ultrastructural detection of production of H2O2. A significant direct effect of both human and murine IL-5 on granulocyte oxidative metabolism could only be detected in those patients with AD and allergic rhinitis. Also, as compared to normal controls, significantly increased CL responses were observed in these patients with stimulation with other granulocyte-activating cytokines, particularly GM-CSF. In patients with psoriasis there was no significant increase in response to stimulation with TNF alpha, TNF beta or GM-CSF, but IL-5 induced slight but significant CL responses in the granulocytes. None of the cytokines tested significantly stimulated the release of ECP in any of the groups. Ultrastructural studies showed that stimulation with human as well as murine IL-5 produced significant morphological changes in both eosinophils and polymorphonuclear neutrophilic granulocytes from the patients with AD. Production of H2O2 was visualized at the luminal part of the intracytoplasmic vesicles of the granulocytes and at the points of contact between the cells. On morphometric analysis, almost all the polymorphonuclear neutrophils in the patients with AD appeared to be activated, whereas only some of these cells in the normal controls showed signs of activation.