Abstract:

Objective To observe the immune response of mouse Th17 cells from mesenteric lymph node (MLN) after treatment with soluble egg antigens (SEA) and soluble adult antigens (SWA) of Schistosoma japonicum. Methods Two New Zealand white rabbits were infected with S. japonicum cercariae through abdominal skin attachment for 20 min. After 45 days, SWA and SEA were collected. Twenty C57BL/6 mice were randomly divided into the infection group and the healthy group (n = 10 in each group). The mice in the infection group were infected with 40 ± 5 worms of S. japonicum through the abdominal skin. At 5 to 6 weeks, the serum levels of SEA- and SWA-specific IgG were determined by ELISA. The MLN lymphocytes were isolated and divided into four groups. Lymphocytes in group A received no stimulation, those in group B were treated with 100 μg/ml SEA + 1 μg/ml anti-CD28 mAb, those in group C were treated with 100 μg/ml SWA + 1 μg/ml anti-CD28 mAb, and in group D they were treated with 1 μg/ml anti-CD3 mAb + 1 μg/ml anti-CD28 mAb. The levels of IL-17 and IFN-γ in the supernatant were detected by ELISA after 72 h treatment, and Th17 cells were detected by flow cytometry after 9 h treatment. Results ELISA results showed that the A₄₅₀ values for serum SEA- and SWA-specific IgG in the infection group (2.66 ± 0.20, 1.68 ± 0.66) were both significantly higher than those of the healthy mice (0.19 ± 0.05, 0.25 ± 0.12, respectively) (P < 0.01). Flow cytometry showed that the proportions of CD4⁺IL-17⁺ cells and CD4⁺IFN-γ⁺ cells in group B lymphocytes from infected mice (0.43% and 0.56%, respectively) were significantly higher than the healthy group (0.05% and 0.20%) (P < 0.05). Similar results were found for group C (0.39% and 0.76% vs. 0.04% and 0.19%) (P < 0.05). The levels of IFN-γ and IL-17 were (49.13 ± 14.71) and (41.73 ± 2.42) pg/ml, respectively in group B lymphocytes from infected mice, which were significantly higher than the (3.27 ± 0.33) and (9.22 ± 0.58) pg/ml in healthy mice (P < 0.01). Similar results were found in group C [(46.92 ± 16.73) and (36.14 ± 4.82) pg/ml vs. (3.38 ± 0.34) and (8.78 ± 0.93) pg/ml] (P < 0.01). The IL-17 level in group B was (41.72 ± 2.42 ) pg/ml, significantly higher than the (36.14 ± 4.82) pg/ml in group C. Conclusion Both SEA and SWA can induce secretion of IL-17 and IFN-γ from MLN lymphocytes of C57BL/6 mice infected with S. japonicum, and the secreted IL-17 is significantly higher for SEA than SWA. SEA and SWA can also induce the production of CD4⁺IL-17⁺ cells and CD4⁺IFN-γ⁺ cells in the mesenteric lymph nodes of C57BL/6 mice infected with S. japonicum.

Key words: Schistosoma japonicum, Mesenteric lymph node, Soluble egg antigen, Soluble adult antigen, Th17