Pharmacological evidence supporting a role for IL-1, IL-2 and serotonin in the inflammation induced by Schistosoma mansoni Soluble Egg Antigen (SEA) in rat paws

THIS study intended to characterize pharmacologically the mediator(s) released in the inflammation induced by Soluble Egg Antigen (SEA), the main antigen released from eggs of Schistosoma mansoni, in rat hindpaws. A single intraplantar injection of 0.1-100 mu g SEA at day zero induced a dose-dependent increase in the volume of rat hindpaws characterizing an oedema of quick onset (within 15min) and 4h-duration, which was confirmed by histopathological analysis of the paws. A second injection of SEA in the same paw (1-10 mu g) 28 days later induced an increased dose-dependent oedematogenic response. The early oedematogenic response following SEA sensitization was derived from serotonin release and interleukin-1 (IL-1), since treatment with either pizotifen or an antibody against IL-1, reduced the response by 60% and 48%, respectively. The increased oedematogenic response derived from SEA-challenge (10 mu g) of rat paws derived from a local rather than systemic reaction, since it was not observed if the sensitization was in the contralateral paw or the peritoneal cavity of the animals. Chronic treatment with inhibitors of IL-2 synthesis/release such as cyclosporin or dexamethasone during the sensitization phase reduced the oedematogenic response due to SEA challenge by 51% and 55%, respectively. These data suggested that SEA-challenge was immune-derived and dependent of IL-2 release. It is discussed the association between cytokine release and the resistance of rats to S. mansoni infection.