Interestingly, TNF-α deficiency does not affect the mechanisms involved in host defenses against Giardia infection, which includes the generation of IgA, the proliferation of mast cells, and the secretion of IL-6 or IL-4, suggesting that TNF-α does not exert its effects through these mechanisms mentioned previously in control of Giardia, but through other effector responses downstream of it (Zhou et al., 2007). This evidence concerns the gene IL4 and giardiasis.