Abstract: Objective To observe the phenotype changes of Kupffer cells in the progression of hepatic schistosomiasis japonica. Methods Twenty male BALB/c mice at 6 weeks of age were infected with 16 cercariae of Schistosoma japonicum via a percutaneous route, then sacrificed at 0, 21, 32, 42 and 52 days after infection to collect liver samples for pathological observation by HE staining and Masson’s triple staining, and qPCR was used to detect the expression of Th1- [interferon-γ (IFN-γ) and tumor necrosis factor-α (TNF-α)] and Th2-type [IL-4 interleukin-4 (IL-4), IL-13 and IL-10] cytokines, as well as M1- [inducible nitric oxide synthetase (iNOS), cluster of differentiation 16(CD16) and IL-6] and M2-type [arginase 1 (Arg-1), CD206 and IL-10] markers of macrophages differentiated from Kupffer cells. Meanwhile, the Kupffer cells were treated with IFN-γ or IL-4 in vitro (0, 5, 25 and 50 ng/ml for 12 h; 25 ng/ml for 0, 12, 24 and 36 h), and the expression of M1- and M2-type markers was detected again by qPCR. Results HE staining and Masson’s triple staining revealed that the deposition of parasite eggs began to appear in the liver tissue from day 32 post-infection, and the formation of egg granulomas and fibrosis were observed on day 42 post-infection. qPCR results showed that the expression of IFN-γ in the liver tissue peaked on day 32 (29.243 ± 3.245) post-infection, and decreased sharply to 8.923 ± 3.002 on day 52 (P < 0.05 vs. day 0). The expression of IL-4 peaked on day 42 (25.521 ± 4.957), and that of IL-13 on day 52 (50.793 ± 9.631) (both P < 0.05). The expression of iNOS increased to 2.950 ± 0.321 on day 42, followed by a decrease to 1.783 ± 0.319 on day 52. The highest expression of Arg-1 was found on day 52(2.003 ± 0.152; P < 0.05). After 12 h treatment with 5, 25, and 50 ng/ml IFN-γ, the relative expression levels of iNOS, IL-6 and CD16 in Kupffer cells were dramatically elevated to 54.690-68.577, 1.887-2.427 and 2.417-2.787, respectively (P < 0.05 vs. control group), while those after 25 ng/ml IFN-γ treatment for 12, 24 and 36 h were 34.810-109.210, 10.327-15.143, and 1.887-3.317, respectively. However, no significant changes were found for Arg-1. The relative expression levels of Arg-1, IL-10 and CD206 were elevated significantly(9.153-24.253, 1.923-3.687 and 37.770-72.133, respectively) after 12 h treatment with 5, 25 and 50 ng/ml IL-4(P < 0.05), while those after 25 ng/ml IL-4 treatment for 12, 24 and 36 h were 3.563-12.613, 1.637-2.673, and 19.732-71.943. No significant changes were found for iNOS. Conclusion The Kupffer cell phenotype switches from M1 type in the early phase of infection to M2 type in the later period of infection, indicating a close relationship between Kupffer cell differentiation and liver immune microenvironment.

Key words: Schistosomiasis, Granuloma, Fibrosis, Kupffer cell