Effect of diethylcarbamazine on serum-dependent cell-mediated immune reactions to microfilariae in vitro

The effect of diethylcarbamazine citrate (DEC) on serum-dependent cellular adherence and cytotoxicity to sheathed and exsheathed microfilariae of Litomosoides carinii and Brugia pahangi in vitro has been investigated. DEC at 5 micrograms/ml promoted antibody-mediated neutrophil adherence and cytotoxicity with sheathed L. carinii microfilariae. With exsheathed parasites, the drug promoted significantly complement-and antibody-mediated cellular adherence and cytotoxicity. In the case of B. pahangi, antibody-dependent cell-mediated cytotoxicity (ADCC) of neutrophils to sheathed and exsheathed microfilariae were similarly stimulated by DEC. Pre-incubation of microfilariae with DEC promoted the cellular adherence and cytotoxicity whereas pre-incubation of cells had no such effect. DEC stimulated the adherence of eosinophils to both sheathed and exsheathed microfilariae of the two species but the adherence resulted in cytotoxic effect only on the L. carinii microfilariae. DEC at higher concentrations (100 or 500 micrograms/ml) inhibits these processes. Data on the role of different serum factors involved in this phenomenon have been presented and discussed.