Alteration of T cell subtypes in spleen and antibodies of serum in mice infected with Angiostrongylus cantonensis.

The immune responses of Angiostrongylus cantonensis infection are closely relevant to the host's self-protection and the nematode's pathogenesis. In the present study, BALB/c mice were randomly divided into uninfected control group, infection group 1, and infection group 2. The infection group 1 and infection group 2 were infected with 20 and 40 third-stage larvae of A. cantonensis per mouse, respectively. The splenocytes from the mice were collected and cultured on the 19th and 25th days post-infection; the subtypes of T cells in splenocytes were detected by flow cytometry with fluorescence staining method, and the cytokines in cultured supernatants of splenocytes were assayed by the method of ELISA. The specific IgG and IgE antibodies in sera of the mice were periodically detected by ELISA. The results showed that the percentages of CD4(+) and CD4(+) IL-4(+) T cells in splenocytes of infected mice were much higher (P < 0.05) than those in control mice; however, the percentages of CD4(+) IL-17(+) and CD4(+) IFN-γ(+) T cell were much lower(P < 0.01) after the infection. The levels of CD8(+) T cells in infected mice also rose, but differences between control mice and infected mice were not significant. In comparison with control mice, the concentration of IL-4 in the cultured supernatants of splenocytes in infected mice increased significantly (P < 0.05), but that of IL-17 decreased significantly (P < 0.01). In addition, the number of larvae infected and days after infection may influence levels of the T cell subtypes and the cytokines in spleen, too (P > 0.05). On humoral immunity, the levels of specific IgG antibodies in sera rose a bit at the fifth day post-infection, and reached a peak at the 20th day post-infection; the specific IgE antibodies gradually heightened during first 10 days post-infection; then, it showed a downward trend during the 15th to 25th days post-infection. It is evident that the percentages of CD4(+) T lymphocytes of spleen in the mice infected with A. cantonensis markedly increase and polarize to Th2 phenotypes, and the function of Th17 cells is inhibited. In addition, the elevation of specific IgG antibodies in sera of the infected mice is more significant than that of specific IgE antibodies.