T-cell activity associated with secondary infections and implanted cysts of Echinococcus granulosus in BALB/c mice.

Selected cytokine profiles of lymphocytes were assessed in BALB/c mice infected with protoscoleces of Echinococcus granulosus. Late stages of the infection (three months+) were characterized by more dominant Th2 activity with elevated IL-4 and IL-10 and reduced IFN-gamma output by Con-A and antigen stimulated splenocytes. Circumparasitic leucocytes produced mainly IL-10 by five months post infection. A peak in IFN-gamma production in the first month of infection may suggest Th1 or Th0 activity at this time and this may be correlated with initial protoscolex death. In addition, cytokine profiles from mice implanted with intact hydatid cysts were also assessed. At two weeks post implantation all cysts were still viable and cytokine production was characterized mainly by elevated IL-10 production. However, at four months post implantation, some of the cysts from two mice had been killed whilst all cysts in the remaining mouse remained viable. In the mice where dead cysts were present, elevated levels of IFN-gamma were detected from splenocytes and circumparasitic cells. Elevated IL-4 was also evident with the splenocytes. In the mouse with viable cysts IFN-gamma production was reduced Results indicate that IFN-gamma(Th1) activity may be correlated with killing of both protoscoleces and established cysts of E. granulosus.