IMMUNOMODULATION BY HYDATID CYST FLUID TOXIN (ECHINOCOCCUS-GRANULOSUS)

Since the experimental infection by hydatid cysts (Echinococcus granul osus) in mice causes immunomodulation of the host, the effects of hyda tid fluid (HF) and fractions of HF were compared in vitro and in vivo. Fractions of HF were obtained using ammonium sulphate precipitation, chloroform/methanol extraction and thin-layer chromatography (TLC). HF proved to be toxic to murine peritoneal macrophages in vitro, and whe n macrophages were incubated with the different fractions of HF, most toxicity was found in a single TLC-purified function with an adjuvant- like effect on the production of specific antibodies against bovine al bumin and human red blood cells in mice. Treatment of mice with the to xin caused a drop in the percentage of peripheral blood lymphocytes. F low-cytometric analysis showed that T-cells from toxin-treated mice ha d lower membrane-CD3, CD4 and CD8 density, and had higher percentages of CD8(+) splenocytes and CD4(+) thymocytes expressing CD25. The toxin caused a down-regulation of CD4 and CD8 expression on thymocytes in v itro, that was dependent on the presence of macrophages. The results m ay attribute to these toxins a role in the host-parasite relationship of hydatidosis.