Kinetics of Serum and Cellular Interleukin-5 in Posttreatment Eosinophilia of Patients with Lymphatic Filariasis

Peripheral blood eosinophil counts and serum levels and in vitro production of eosinophilopoetic cytokines were assessed before and at frequent intervals after diethylcarbamazine treatment of Bancroftian filariasis. Eosinophil counts peaked at day 7 after the start of treatment (359% ± 118% of pretreatment levels) and declined to pretreatment levels by day 17. Serum interleukin (IL)-5, undetectable in 14 of 15 patients before treatment, rose sharply but transiently, with peak levels (32 ± 7 pg/rnl.) 2 days after diethylcarbamazine treatment. Granulocytemacrophage colony-stimulating factor and IL-3 were not detectable in serum at any time. In vitro mitogen-induced IL-5levels decreased significantly in 7 of9 patients 3 days after treatment when serum IL-5 was at near-peak levels. By day 10 IL-S values increased in 8 of 9 patients compared with treatment values (P < .02). These data define the temporal relation between serum IL-S levels and the subsequent development of eosinophilia and suggest that lymphocytes are the source of IL-S.