• Giardia lamblia;
  • TNF;
  • trans-epithelial electrical resistance


Giardia lamblia is a ubiquitous parasite that causes diarrhoea. Effective control of Giardia infections in mice has been shown to involve IgA, T cells, mast cells and IL-6. We now show that Tumour necrosis factor α (TNFα) also plays an important role in the early control of giardiasis. Mice treated with neutralizing anti-TNFα antibodies or genetically deficient in TNFα were infected with the G. lamblia clone GS/(M)-H7. In both cases, mice lacking TNFα had much higher parasite numbers than controls during the first 2 weeks of infections. However, anti-parasite IgA levels, mast cell responses, and IL-4 and IL-6 mRNA levels do not appear significantly altered in the absence of TNFα. In addition, we show that mice infected with G. lamblia exhibit increased intestinal permeability, similar to human Giardia infection, and that this increase occurs in both wild-type and TNFα deficient mice. We conclude that TNFα is essential for host resistance to G. lamblia infection, and that it does not exert its effects through mechanisms previously implicated in control of this parasite.