The differential release of eosinophil granule proteins. Studies on patients with acute bacterial and viral infections

Background: Harlier in vitro studies have suggested that the eosinophil may release its granule proteins selectively depending on the stimulus to which the cell is exposed. Objective: The object of the present study was to study the question of selective release in vivo by means of serum measurements of the two eosinophil granule proteins eosinophil cationic protein (ECP) and eosinophil peroxidase (EPO) in acute infections. Methods: Fourty-six subjects with acute infections were studied before treatment, 20 with bacterial infections and 26 with viral infections. Serum ECP, EPO and MPO were measured by specific RIA. Results: In acute bacterial infections ECP, but not EPO. was significantly raised in serum (P < 0.0001) compared with non-infected healthy subjects. In acute bacterial infections ECP was significantly correlated to the levels of the neutrophil marker myeloperoxidase (MPO) (r_s= 0.96, P < 0.0001) but not to EPO. In acute viral infections neither ECP nor EPO were on average raised. However, almost 20% the patients had elevated levels of both proteins. In the viral infections the serum-levels of ECP and EPO were correlated (r_s= 0.63, P < 0.001), but no correlation was found with MPO Conclusion: It is concluded that eosinophils are activated during acute bacterial infections and that this activation results in the preferential mobilisation of ECP. The simultaneous assay of the two eosinophil proteins, ECP and EPO. may give new insight into the role of the eosinophil in disease.