DEXTRAN SEDIMENTATION INDUCES A DIFFERENCE IN THE PERCENTAGE OF HYPODENSE EOSINOPHILS IN PERIPHERAL-BLOOD BETWEEN CHILDREN WITH ALLERGIC-ASTHMA AND HEALTHY CONTROLS

Considerable differences in the percentage of hypodense eosinophils in the peripheral blood of asthmatics have been reported by different in vestigators. In these previous studies dextran sedimentation was used for removal of erythrocytes prior to density centrifugation. We hypoth esized that the sedimentation procedure might induce the presence of h ypodense eosinophils in the peripheral blood of asthmatic patients. In order to test this hypothesis, we compared eosinophil density profile s from peripheral blood of children with asthma and of age-matched hea lthy controls, using different procedures. In the first method (direct method) blood samples were directly layered on a discontinuous Percol l gradient. Erythrocytes were removed by isotonic lysis. In the second method (dextran sedimentation) erythrocytes were removed by sedimenta tion with dextran prior to gradient centrifugation. Results of the dir ect method show no significant difference in percentage of hypodense e osinophils between children with asthma and healthy controls (9.19% an d 6.84% respectively). However, after dextran sedimentation, children with asthma had a significantly higher percentage of hypodense eosinop hils than healthy controls (15.40% and 8.84% respectively; P < 0.05). The percentage of hypodense eosinophils was correlated with the number of eosinophils and with the lung function, measured as the Tiffeneau index (FEV(1)/VC), in the whole group of subjects when the direct meth od was used. We conclude that an increased percentage of hypodense eos inophils is not present in the circulation of children with asthma, bu t can be induced in vitro by dextran sedimentation. Therefore, in vitr o generation of hypodense eosinophils in the blood of patients with as thma seems to be related with the primed state of eosinophils.