DOSE-DEPENDENT EFFECTS OF HYDATID FLUID TOXINS FROM ECHINOCOCCUS-GRANULOSUS ON MOUSE PERITONEAL-MACROPHAGES

Hydatid fluid (HF) from hydatid cysts of the cestode Echinococcus gran ulosus inhibited the phagocytosis of bacteria and yeast cells by host macrophages in vitro. Different assays were used to study the dose-dep endent effect of partially purified HF toxins on peritoneal macrophage s (PMo) of the mouse. Trypan blue exclusion, as well as measuring the specific release of lactate dehydrogenase activity and Cr-51 release o f Cr-51-labelled PMo, showed that incubation with HF toxins lead to th e lysis of the target cells. By measuring the effect of the toxins on the reduction of [4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium br omide by PMo, and by experimental labelling using [H-3]-uridine, a dec rease in metabolic activity was seen. However, at non-lytic concentrat ions, the PMo showed a peak of metabolic activity. The observations of the effects on macrophages by parasite-derived toxins may be related to a mechanism by which the parasite survives within an immunized host .