Elevated IL-5 levels in pleural fluid of patients with paragonimiasis westermani

To investigate the pathogenic mechanisms of eosinophilic pleural effusion i n patients with paragonimiasis, we measured the levels of IL-5, granulocyte -macrophage colony-stimulating factor (GM-CSF) and interferon-gamma (IFN-ga mma) in pleural effusions. Samples were obtained from 11 patients with Para gonimus westermani infection. In addition, samples from 12 patients with pl eural transudates, 16 with tuberculous pleurisy, seven with empyema and 20 with lung cancer were also examined. Eosinophilia was remarkable in periphe ral blood (range 4-34%, median 23.4%) and pleural fluid (range 0-95%, media n 71%) of paragonimiasis patients. IL-5 concentrations in pleural effusions of paragonimiasis were markedly higher than those in other groups. Althoug h marked elevation of GM-CSF and IFN-gamma levels was observed in pleural e ffusion of empyema and tuberculosis patients, it was marginal in the pleura l effusion of paragonimiasis patients. In paragonimiasis patients, IL-5 lev els in the pleural effusion correlated well with the percentage of eosinoph ils in peripheral blood and pleural fluid. Such a correlation was not obser ved between GM-CSF levels in pleural effusion and percentages of eosinophil s in pleural fluid or peripheral blood. Our findings suggest that in parago nimiasis IL-5 in the local inflammatory site is particularly important in m ediating eosinophilia in peripheral blood and pleural effusion.