Early hepatic cytokine mRNA expression in experimental rat fasciolosis

We studied the development of the cellular response, particularly with respect to Th1 and Th2 cytokine mRNA levels, in rat liver during the first 14 days of experimental infection with Fasciola hepatica. We analysed the panel of cytokines involved in initiation of the inflammatory and immune response. The levels of various mRNAs, particularly those primarily associated with the acute inflammatory response, and those commonly associated with T-cell proliferation and differentiation, were assessed by reverse transcription-polymerase chain reaction (RT-PCR) in liver samples. We also investigated the immune and inflammatory mediators balance in the liver, draining lymph node and spleen, by RT-competitive PCR quantification of mRNA levels for IL-4, IL-10 and IFN-gamma. Our data provide the first evidence that, in the early phase of infection, the inflammatory response in the liver of infected animals is transiently depressed or delayed. A Th0 profile was initially observed in the liver and hepatic lymph node, which developed into a Th2 profile 2 weeks after infection in the liver only. In the spleen, cytokine down-regulation was initiated and maintained during this period, suggesting that the parasite acts differently locally and in the periphery.