Eosinophilia in children. Cytochemical and immunological analysis of increased eosinophils.

Cytochemical and immunological studies of increased eosinophils were performed in three children with marked eosinophilia. These children were diagnosed as having non-Hodgkin's lymphoma, transient eosinophilia, and hyper-eosinophilic syndrome. All showed marked eosinophilia, with eosinophil counts of more than 5,000/mm3 in the peripheral blood and with eosinophils in all maturational stages in the bone marrow. In contrast to normal eosinophils, the increased eosinophils in three patients on cytochemical analysis showed moderately to strongly positive reactions for staining with alpha-naphthyl-butyrate esterase. Also, the mature eosinophils in the patient with lymphoma showed a strongly positive reaction for periodic acid-Schiff staining. The positive reaction for alpha-naphthyl-butyrate esterase and periodic acid-Schiff stain indicates the presence of eosinophilic proliferative disorders in these cases. Surface marker analysis of peripheral eosinophils demonstrated that an increased proportion of eosinophils expressed My7, a marker of granulocytes, in two patients with transient eosinophilia or hyper-eosinophilic syndrome, but not in a patient with lymphoma. In addition, 30-40% of eosinophils expressed Ia antigen, a differentiation marker of eosinophils, in two patients with lymphoma or hypereosinophilic syndrome. Thus, eosinophils in transient eosinophilia showed mature features, and those in hypereosinophilic syndrome showed immature features immunologically. Whereas, eosinophils in lymphoma may have a dysmaturity on the expression of Ia and My7. Cytochemical and immunological analyses of increased eosinophils may play an important role in clarifying the etiology of eosinophilia, especially its association with malignancy or other proliferative disorders.