Altered density, metabolism and surface receptors of eosinophils in eosinophilia

A comparison was made between eosinophils from normal persons and patients with eosinophilia. Highly purified eosinophils were obtained by centrifugation in a Percoll density gradient. Studies were carried out on density distribution, oxygen consumption upon adherence to serum-coated Sephadex and expression of cell surface receptors for IgG and complement. In eosinophil leukaemia the density of eosinophils was abnormally low. Abnormal light density fractions of blood eosinophils were also detected in the hypereosinophilic syndrome (HES). Light density eosinophils of HES showed morphological signs of degranulation consonant with the finding of a low content of granular eosinophil cationic protein (ECP) suggesting degranulation in the circulation or abnormal granule formation in the marrow. In addition, such cells exhibited a higher oxygen consumption than eosinophils with normal density upon adherence to serum-coated Sephadex. Low density eosinophils showed a greater number of cells with Fc-IgG and complement receptors than high density cells. Likewise exudate eosinophils displayed an abnormally low density with higher than normal oxygen consumption indicating that eosinophils may be activated in the tissues. In one patient with HES, a febrile episode resulted in a disappearance of eosinophils with a normal density while abnormal low density eosinophils increased. Our findings suggest that eosinophils from some patients with eosinophilia may be 'activated' in the circulation.