Studies on blood eosinophils. II. Patients with Löffler's cardiomyopathy.

Studies were done on blood eosinophils from four patients with raised blood eosinophil counts and heart failure. In three of the patients cardiological studies demonstrated the distinctive endocardial lesions and restrictive cardiomyopathy of Löffler's endocarditis and endomyocardial fibrosis. The fourth patient died with similar symptoms and signs. In blood films it was found that all four had more than 1 X 10(9) eosinophils per litre which were vacuolated and contained reduced numbers of crystalloid granules which were also shown to have ultrastructural changes. Unlike eosinophils from normal individuals the patients' eosinophils possessed receptors for rabbit IgG-coated erythrocytes and actively phagocytosed erythrocytes coated with rabbit IgG or human C3b. It is concluded that in these patients, a large proportion of the circulating eosinophils had developed characteristics of mature or stimulated eosinophils. This enabled them to respond to soluble substances in the bloodstream by forming endocytic vacuoles which led to degranulation of the crystalloid granules. These studies, taken in conjunction with other recent work in this field, support the concept that the restrictive cardiomyopathy of hypereosinophilic states, including Löffler's endocarditis and endomyocardial fibrosis, is a result of prolonged release of products from degranulated eosinophils while they are in the circulation.