Expression of IL-4, IL-10 and IFN-γ in the liver tissue of cattle that are naturally infected with Fasciola hepatica.

The role of interleukin IL-4, IL-10 and interferon gamma cytokines on natural Fasciola hepatica infection was investigated by quantifying the mRNA levels in liver tissue from chronically infected cattle. IL-4 and IL-10 had higher expression relative to interferon gamma in the liver tissue of infected animals when compared with the control group. The higher levels of IL-10 and IL-4 observed in the present study suggest a synergism between these cytokines, as well as involvement in the suppression of TH1 cell responses and a consequent induction of decreased interferon gamma expression in chronic cattle fascioliasis. The cytokine ratios were positively correlated, indicating a predominance of IL-4 in the chronic phase of infection with respect to interferon gamma and IL-10. Interferon gamma was predominant expressed in the controls, suggesting the involvement of IL-10 in modulating the immune response in favor of IL-4 in infected animals. Our results suggest that the TH2 polarized host immune response previously observed in experimental infection may also be responsible for establishing chronic phase and the maintenance of the natural infection of cattle from endemic areas that are in continuous contact with parasite.