In vivo expression of cytokine mRNA in rats infected with Schistosoma mansoni

As an animal model, rat schistosomiasis mansoni has provided considerable k nowledge of immune mechanisms involved in the expulsion of worms and in a s ubsequent development of immunity to reinfection. Although it is clear that ADCC mechanisms participate in immunity to reinfection; the nature of the cytokines involved in immunity is unknown. To analyse the pattern of cytoki nes involved, the mRNA levels of different cytokines were assessed by RT-PC R as they occur within tissues during the course of infection. In spleens f rom infected rats, a significant elevation in IL-2 and IL-5 mRNA was observ ed during the early phase of infection (day 7). Analysis of pulmonary cytok ine responses showed a dramatic increase in IL-4 and IL-5 on day 7. This wa s accompanied with a low but significant increase in IL-2 (day 11) and IL-1 2 (day 7) in the absence of augmented IFN-gamma expression. The cytokine ex pression patterns of draining lymph nodes (LN) from infected rats showed a significant increase of IL-2, IL-4 and IL-5 on day 21. Analysis of IL-10 ex pression showed exclusively a significant increase in LN on day 11. IFN-gam ma mRNA was nor detected in any tissue sample. Thus, rats develop a predomi nately Th2-type cytokine response during a primary infection which may be i nvolved at least in part, in the expression of immunity against Schistosoma mansoni infection.