| Summary: | 碩士 === 國立陽明大學 === 寄生蟲學研究所 === 87 === Schistosomiasis is endemic in 74 countries and about 200 million people are estimated to be infected. Schistosomiasis is listed as the second most important tropical diesase by the World Health Organization, second only to malaria. In order to investigate the host immune response and to analyze the type, activity and the kinetics of Th1 and Th2 cytokine response in Schistosoma japonicum infection, C57BL/6 mice were infected with 30 cercariae of Anhui strain or Hubei strain of S. japonicum. The mice were sacrificed at 3, 5, 7, 8, 10, 12 and 20 wk postinfection. The mRNA gene expressions were detected with the reverse transcription-polymerase chain reaction (RT-PCR). Six cytokines: IFN-γ, IL-2, IL-4, IL-10, TNF-α, TGF-β, and one synthase iNOS were evaluated. When mice were infected with Anhui strain of S. japonicum, the results showed that IL-2 mRNA level increased gradually at 3-5 wk and reached the peak at 7 wk postinfection, then decreased markedly. However, the IL-2 mRNA level reached the peak at 3 wk postinfection if mice were infected with Hubei strain of the parasite. The kinetic patterns of the other five cytokine gene expression on both strains were very similar. Both IFN-γ mRNA increased significantly at 3-5 wk, started to decrease at 7 wk, the minimum level occurred at 12 wk postinfection. IL-4 and IL-10 mRNA increased markedly at 7-10 wk, then decreased at 12 wk, 20 wk had lowest level. TNF-α mRNA increased significantly on both early stage (3-5 wk) and acute infection stage (7-10 wk), began to decrease at 20 wk. TGF-β mRNA started to increase at 3 wk, then rise markedly at 5 wk, both reached maximun at 7 wk. The iNOS gene expression was not obvious before the first 5 wks but increased suddenly and reached a maximum at 7 - 12 wk, then decreased significantly at 20 wk.
This study showed that early stage immune response is relevant to Th1 cells and macrophages when mice were infected with Chinese strain of S. japonicum. At acute stage, Th2 cells and macrophages play the major role. The down-regulation of Th1 cells were induced by Th2 cell cytokines. However, during the chronic stage, Th2 cytokine gene expression became very low, therefore, infected mice may have "spontaneous modulation" in which the granulomatous response to tissue deposited eggs was gradually tempered. The iNOS gene expression were regulated by TNF-α and IFN-!.
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