Pattern of circulating eosinophils in allergic children suffering from infectious disease

BACKGROUND AND AIM: Both bacterial and viral acute infections are accompanied by a typical fall in the number of circulating eosinophils followed, at remission, by a rapid return to starting values. The aim of this study was to check whether this typical pattern can be observed in atopical children. MATERIALS AND METHODS: A retrospective study was performed in a group of atopical subjects (mainly asthmatic) suffering from intercurrent infectious diseases (mainly bronchopneumonia); circulating eosinophils were assayed during the acute phase of disease and during remission. The control group consisted of 21 atopic children without signs or symptoms of infectious diseases. RESULTS: The mean number of circulating eosinophils was 412.6 +/- 199.8 in the control group of allergic children 25.1 +/- 39.7 in the group with acute infectious diseases and 241 +/- 137.5 in the group of children with infectious diseases during remission. The differences between the group of children with infectious diseases and that in remission were statistically significant. The typical pattern of the fall and rise of circulating eosinophils was observed in 9 out of 10 children with acute infections. The cut-off proposed as the discriminating factor between acute phase infection and subjects in remission or without infectious diseases was 100 eosinophils/mm3. CONCLUSIONS: During the course of infective pathologies in allergic subjects there is an abrupt and significant reduction in circulating eosinophils followed, during remission, by a return to levels comparable to those in controls. Eosinophil assay therefore appears to be a useful parameter to monitor acute infection in allergic subjects. In particular, increased eosinophil levels are an early indicator that the infection has been overcome and remission is in progress. The authors repropose the hypothesis that eosinophils play a double role that alternates between activating the allergic phlogosis and eliminating non-allergic phlogosis, depending on the cytokinic context in which this occurs.