RESUMO
Cercariae were obtained in a large number from the maintained life cycle of S. mansoni. They were attenuated at different doses [20 Kr, 50 Kr,60Kr, 70 Kr and 80 Kr] of gamma radiation. Laboratory bred Swiss Albino mice were classified into 7 groups. Five groups were immunized with +/- 500 S. mansoni cercariae. Two groups were used as positive and negative controls. All animals were sacrificed after 8 weeks. Spleen cell proliferative responses to Phytohaemagglutinin [PHA] were assessed in all groups. IL-10 was measured by ELISA in serum and splenic cells secretion in vitro. RNA extracted from freshly isolated liver cells was analyzed for detection of m RNA of IL-10 by reverse transcriptase polymerase chain reaction [RT-PCR]. The results showed augmentation of proliferative cell from the spleen in all vaccinated groups except with 80 Kr. irradiated cercariae group. The highest percentage of lymphocytes transformation was recorded among the mice immunized with 60 Kr. irradiated cercariae. After challenge, splenic reasponses in all groups declined progressively to the control level. IL-10 secretion from spleen cells of all vaccinated groups increased after challenge with the least level in 60 Kr. immunized challenged group IL-10 m RNA expression was higher among 60 Kr. immunized with irradiated cercariae group than 70 Kr. one, but with no expression among 80 Kr. cercariae immunized ones