Eosinophil membrane antigens: phenotypic frequencies in normal individuals and patients with the hypereosinophilic syndrome.

The membrane antigen phenotype of eosinophils from six normal individuals and eight patients with the hypereosinophilic syndrome (HES) were examined to see whether subpopulations of eosinophils exist. Experiments were done with a panel of 6 monoclonal antibodies, using the fluorescent activated cell sorter, and immunocytochemistry. All six antibodies bound eosinophils and neutrophils, but not lymphocytes, monocytes, platelets or erythrocytes. The phenotypic frequencies of five of the six antibodies were increased in patients' eosinophils (p less than 0.005). This increase was associated with the intermediate-density eosinophils, while the antigen detected by antibody Eon 7 was associated with the light-density eosinophils. Normal eosinophils could be induced to increase their expression of these membrane antigens by incubation with mononuclear cell supernatants which are known to increase the cytotoxic capacities of eosinophil, 'activation'. It was concluded that there is a single eosinophil which undergoes post-mitotic differentiation in the blood, leading to activation and degranulation. The heterogeneity seen in patients' eosinophils reflect different stages of cell maturation and activation.