INTERLEUKIN-7 IN THE SKIN OF SCHISTOSOMA-MANSONI-INFECTED MICE IS ASSOCIATED WITH A DECREASE IN INTERFERON-GAMMA PRODUCTION AND LEADS TO ANAGGRAVATION OF THE DISEASE

The effect of recombinant interleukin-7 (rIL-7) on the course of murin e schistosomiasis and the development of the accompanying immune respo nse were investigated. We demonstrated that IL-7 expression could be d etected in the skin of infected mice from 1 to 21 days following infec tion. We here report that intradermal injection of exogenous human IL- 7, prior to the penetration of the parasite into the skin, leads to a more severe liver pathology and an increased number of surviving adult parasites. In addition, injection of rIL-7 alters parasite migration (estimation of burdens of young larvae in lungs and liver). Administra tion of rIL-7 led to a decrease of IL-12 and interferon-gamma- (IFN-ga mma) specific messengers RNA in skin and, more markedly, in skin-drain ing lymph nodes. The number of B220 expressing cells was increased, an d T-cell number was reduced, in IL-Ti-treated infected mice. In additi on, levels of IFN-gamma and IL-4 in sera were significantly reduced, w hereas there was a shift from a Th1 to epsilon. Th2 type associated hu moral response towards the egg antigens. Our experimental observations illustrate that the exogenous administration of rIL-7 affects both th e development of the host's immune response and the behaviour of the p arasite within the infected host. The early and specific production of IL-7 in the host skin, following infection with Schistosoma mansoni, raises fascinating questions concerning the relationships between the parasite and its host at the very beginning of their interaction.