The characteristics of NK cells in Schistosoma japonicum-infected mouse spleens.

Natural killer (NK) cells are classic innate immune cells that play roles in many types of infectious disease. Recently, some new characteristics of NK cells were discovered. In this study, C57BL/6 mice were infected with Schistosoma japonicum for 5-6 weeks and lymphocytes were isolated from the spleen to detect some of the NK cell characteristics by multiparametric flow cytometry. The results revealed that the S. japonicum infection induced a large amount of NK cells, although the percentage of NK cells was not increased significantly. At the same time, the results showed that infected mouse splenic NK cells expressed increased levels of CD25 and CD69 and produced more IL-2, IL-4, and IL-17 and less IFN-γ after stimulation with PMA and ionomycin. This meant that NK cells played a role in S. japonicum infection. Moreover, decreased NKG2A/C/E (CD94) expression levels were detected on the surface of NK cells from infected mouse spleens, which might serve as a NK cell activation mechanism. Additionally, high levels of IL-10, but not PD-1, were expressed on the infected mouse NK cells, which implied that functional exhaustion might exist in the splenic NK cells from S. japonicum-infected mice. Collectively, our results suggest that NK cells play important roles in the course of S. japonicum infection.

Changes in NK and NKT cells in mesenteric lymph nodes after a Schistosoma japonicum infection.

The mesenteric lymph node (MLN) is the main draining lymph node in mouse enterocoelia, which contains many types of immune cells. Among these cells, natural killer (NK) and natural killer T (NKT) cells belong to innate lymphoid cells (ILCs), which have potent activities for controlling a variety of pathogenic infections. In this study, C57BL/6 mice were infected with Schistosoma japonicum for 5-7 weeks. Lymphocytes were isolated from the MLN to detect changes in the phenotype and function of NK and NKT cells using a fluorescence activating cell sorter (FACS). These results demonstrated that a S. japonicum infection could significantly increase the percentage of NK cells in the mouse MLN, (P < 0.05). We found an increase in the cell number of both NK and NKT cells. In addition, we found that NK and NKT cells from infected mice expressed higher levels of CD69 compared to normal mice (P < 0.05). These results demonstrated that a S. japonicum infection could induce MLN NK and NKT cell activation. Moreover, we found that the expression of CD4 was increased in infected MLN NK cells (P < 0.05). Furthermore, intracellular cytokine staining revealed that expression of IL-4 and IL-17 were significantly enhanced in both the NK and NKT cells of infected mice after phorbol 12-myristate 13-acetate (PMA) and ionomycin stimulation (P < 0.05). Taken together, these results indicated that infection-induced MLN NK and NKT cells might play roles in modulating the classical T cell response. Finally, our results indicated that the expression of CD94 was decreased in NK cells, suggesting that the downregulation of CD94 expression might served as a mechanism in NK cell activation.

Characteristics of γδ T cells in Schistosoma japonicum-infected mouse mesenteric lymph nodes.

Gamma delta (γδ) T cells are mainly present in mucosa-associated lymphoid tissues, which play an important role in mucosal immunity. In this study, C57BL/6 mice were infected by Schistosoma japonicum and lymphocytes were isolated from the mesenteric lymph node (MLN) to identify changes in the phenotype and function of γδ T cells using flow cytometry. Our results indicated that the absolute number of γδ T cells from the MLNs of infected mice was significantly higher compared with normal mice (P < 0.05). In addition, the infected γδ T cells expressed a high level of the activated molecule CD69 (P < 0.01) and demonstrated an increasing population of CD4(+) γδ T cells (P < 0.05). MLN γδ T cells secrete interferon-γ (IFN-γ), interleukin (IL)-4, IL-9, and IL-17 in response to propylene glycol monomethyl acetate (PMA) plus ionomycin simulation, and the levels of IL-4, IL-9, and IL-17 increased significantly after S. japonicum infection (P < 0.05). Taken together, these findings indicated that S. japonicum infection could induce γδ T cell activation, proliferation, and differentiation in the MLN. Moreover, our results indicated that the expression of NKG2D (CD314) was not increased in γδ T cells after infection, suggesting that other mechanisms are involved in activating γδ T cells. Furthermore, higher expression of programmed death-1 (CD279) but not IL-10 was detected in the γδ T cells isolated from infected mice (P < 0.05), suggesting that the function of γδ T cells is inhibited gradually over the course of S. japonicum infection.

Roles of Th17 cells in pulmonary granulomas induced by Schistosoma japonicum in C57BL/6 mice.

In schistosomiasis, limited information is available about the role of interleukin-17 (IL-17) in lung, despite the fact that this cytokine plays a crucial role during pro-inflammatory immune responses. In our study, we observed CD4(+)T cells changed after the infection. Furthermore, ELISA and FACS results revealed that Schistosomajaponicum infection could induce a large amount of IL-17 in mouse pulmonary lymphocytes. IL-17-producing cells, including Th17 cells, CD8(+)T (Tc) cells, γδT cells and natural killer T cells, was also associated with the development of lung inflammatory diseases. FACS results indicated that Th17 cell was the main source of IL-17 in the infected pulmonary lymphocytes after phorbol-12-myristate-13-acetate (PMA) and Ionomycin stimulation. Moreover, FACS results revealed that the percentage of Th17 cells continued to increase as over the course of S. japonicum infection. Additionally, cytokines co-expression results demonstrated that Th17 cells could express more IL-4 and IL-5 than IFN-γ. Reducing IL-17 activity by using anti-IL-17 ameliorated the damage and decreased infiltration of inflammatory cells in infected C57BL/6 mouse lungs. Collectively, these results suggest Th17 cells is the major IL-17-producing cells population and IL-17 contributes to pulmonary granulomatous inflammatory during the S. japonicum infection.

TLR7 Modulated T Cell Response in the Mesenteric Lymph Node of Schistosoma japonicum-Infected C57BL/6 Mice.

Toll-like receptors (TLRs) play an important role in regulating immune responses during pathogen infection. However, roles of TLRs on T cells reside in the mesenteric lymph node (MLN) were not be fully elucidated in the course of S. japonicum infection. In this study, T lymphocytes from the mesenteric lymph node (MLN) of S. japonicum-infected mice were isolated and the expression and roles of TLR2, TLR3, TLR4, and TLR7 on both CD4+ and CD8+ T cells were compared. We found that the expression of TLR7 was increased in the MLN cells of S. japonicum-infected mice, particularly in CD4+ and CD8+ T cells (P < 0.05). R848, a TLR7 agonist, could enhance the production of IFN-γ from MLN T cells of infected mice (P < 0.05), especially in CD8+ T cells (P < 0.01). In TLR7 gene knockedout (KO) mice, the S. japonicum infection caused a significant decrease (P < 0.05) of the expression of CD25 and CD69, as well as the production of IFN-γ and IL-4 inducted by PMA plus ionomycin on both CD4+ and CD8+ T cells. Furthermore, the decreased level of IFN-γ and IL-4 in the supernatants of SEA- or SWA-stimulated mesenteric lymphocytes was detected (P < 0.05). Our results indicated that S. japonicum infection could induce the TLR7 expression on T cells in the MLN of C57BL/6 mice, and TLR7 mediates T cell response in the early phase of infection.