Alterations in blood eosinophil morphology, binding capacity for complexed IgG and kinetics in patients with tropical (filarial) eosinophilia

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Abstract
As the significance of the eosinophilia found in some patients with chronic filarial infections is unknown, blood eosinophils were studied in 7 patients with tropical (filarial) eosinophilia who had blood eosinophil counts between 5.2-56.6 .times. 109/l. In 6 of these patients > 20% of the eosinophils were vacuolated and degranulated eosinophils were found in the 3 patients with the most severe illness. In 4 patients serum eosinophil cationic protein levels were raised and serial studies in 2 showed that they returned to normal after treatment with diethylcarbamazine. An increased proportion of eosinophils in these patients were able to bind to complexed IgG suggesting that they were responding to stimuli in the blood and in 1 patient the blood eosinophil half-time clearance was prolonged. Labeled cells were cleared into the spleen, liver and bone marrow. These findings support the hypothesis that in patients with tropical (filarial) eosinophilia, blood eosinophils are induced to release their granule constituents into the circulation. Possibly, these secretion products may interact with microfilariae and may give rise to some of the clinical features of chronic filarial infections.