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

Characteristics of peripheral lymphocyte subsets in patients with different stages of schistosomiasis japonica

Immune cells are important for the development of schistosomiasis japonica and are also critical for the treatment of schistosomiasis. The immune cells in the peripheral blood help assess the immune state. The peripheral lymphocytes in schistosomiasis mansoni were well studied; however, immune cells in patients with different stages of schistosomiasis japonica are not well analysed. Here, we performed a preliminary study to explore characteristics of peripheral lymphocyte subsets in patients with different stages of schistosomiasis japonica. 135 patients with Schistosoma japonicum infection and 25 healthy volunteers were included in this study, including 84 patients with chronic S. japonicum infection and 51 patients with advanced S. japonicum infection. Flow cytometry analysis was performed to evaluate peripheral lymphocytes including T cells, B cells, and natural killer (NK) cells. Blood routine and liver function test data were analysed. Ultrasound examination was used to access liver fibrosis according to the World Health Organization standard about ultrasound in schistosomiasis. Demographic data analysis suggested there was no difference in age and gender in patients with S. japonicum infection and health control group. Liver function tests showed that patients with advanced schistosomiasis had a higher incidence of liver function abnormality and blood lipid than those with chronic schistosomiasis. Blood routine results reflected that haemoglobin, red blood cells, platelets, as well as lymphocytes in the advanced group were significantly less than that in the chronic group. Furthermore, flow cytometry analysis indicated that the percentage of CD4+ T cells was lower in the advanced group, but the percentage of CD19+ B cells was higher in the advanced group. In addition, the number of CD3+ T cells, CD3+ CD4+ T cells, CD3+ CD8+ T cells, and NK cells was less in the advanced group when compared with those in the chronic group. In addition, there was a correlation between the decrease in CD4+ T cells and more severe fibrosis on ultrasound images. Our results indicated that the immune state in the peripheral is different in different stages of S. japonicum infection. Lymphocyte subset analysis has potential to facilitate differential diagnosis of different stages of schistosomiasis japonica and even to be a prognostic factor.

Pattern recognition receptor signaling and innate immune responses to schistosome infection

Schistosomiasis remains to be a significant public health problem in tropical and subtropical regions. Despite remarkable progress that has been made in the control of the disease over the past decades, its elimination remains a daunting challenge in many countries. This disease is an inflammatory response-driven, and the positive outcome after infection depends on the regulation of immune responses that efficiently clear worms and allow protective immunity to develop. The innate immune responses play a critical role in host defense against schistosome infection and pathogenesis. Initial pro-inflammatory responses are essential for clearing invading parasites by promoting appropriate cell-mediated and humoral immunity. However, elevated and prolonged inflammatory responses against the eggs trapped in the host tissues contribute to disease progression. A better understanding of the molecular mechanisms of innate immune responses is important for developing effective therapies and vaccines. Here, we update the recent advances in the definitive host innate immune response to schistosome infection, especially highlighting the critical roles of pattern recognition receptors and cytokines. The considerations for further research are also provided.

Implications of NKG2A in immunity and immune-mediated diseases

In recent studies, NKG2A is revealed to be a key immune checkpoint for both natural killer (NK) cells and CD8⁺ T cells. It form heterodimer receptors with CD94, and targets the peptide-presenting human leukocyte antigen-E (HLA-E) molecules. Upon crosslinking, NKG2A/CD94 delivers inhibitory signals for NK cells and CD8⁺ T cells, while blocking NKG2A can effectively unleash functions of these cytotoxic lymphocytes. The interaction between NKG2A and HLA-E contributes to tumor immune escape, and NKG2A-mediated mechanisms are currently being exploited to develop potential antitumor therapeutic strategies. In addition, growing evidence shows that NKG2A also plays important roles in other immune-related diseases including viral infections, autoimmune diseases, inflammatory diseases, parasite infections and transplant rejection. Therefore, the current work focuses on describing the effect of NKG2A on immune regulation and exploring its potential role in immune-mediated disorders.

Increase in liver γδ T cells with concurrent augmentation of IFN-β production during the early stages of a mouse model of acute experimental hepatitis B virus infection

The role of γδ T cells in acute hepatitis B virus (HBV) infection remains unclear. For the present study, a mouse model of acute HBV infection was constructed using hydrodynamic injection-based transfection of an HBV DNA plasmid (pHBV). Subsequent changes in the percentages of γδ T cells, expression of activation molecules (CD25 and CD69) and the production of the inflammatory cytokines interferon (IFN)-γ and tumor necrosis factor-α (TNF-α) by liver γδ T cells were investigated using fluorescence-activated cell sorting (FACS). Additionally, the immune responses in the mouse liver were evaluated dynamically by measuring cytokine mRNA expression (IFN-α, IFN-β, IFN-γ or TNF-α) using reverse transcription-quantitative PCR, and other populations of immune cells, including CD4⁺T, CD8⁺T, natural killer (NK) or natural killer T (NKT) cells, using FACS. On day 1 following acute HBV infection, the percentage of liver γδ T cells was significantly increased along with the high expression of HBV markers. Additionally, liver γδ T cells displayed peak expression of the activation marker CD69 and peak IFN-γ production within this timeframe. IFN-β mRNA expression and the percentage of NK cells were elevated significantly on day 1 in liver tissues. However, there were no significant changes in the spleen or peripheral γδ T cells. Therefore, these data suggested that during the early stages of acute HBV infection, significantly increased numbers of liver γδ T cells may be involved in the enhanced immune response to the increased expression of HBV markers in the liver.

TLR3 Modulates the Response of NK Cells against Schistosoma japonicum

Natural killer (NK) cells are classic innate immune cells that play roles in many types of infectious diseases. NK cells possess many kinds of TLRs that allow them to sense and respond to invading pathogens. Our previous study found that NK cells could modulate the immune response induced by Schistosoma japonicum (S. japonicum) in C57BL/6 mice. In the present study, the role of TLRs in the progress of S. japonicum infection was investigated. Results showed that the expression of TLR3 on NK cells increased significantly after S. japonicum infection by using RT-PCR and FACS (P < 0.05). TLR3 agonist (Poly I:C) increased IFN-γ and IL-4 levels in the supernatant of cultured splenocytes and induced a higher percentage of IFN-γ- and IL-4-secreting NK cells from infected mouse splenocytes (P < 0.05). Not only the percentages of MHC II-, CD69-, and NKG2A/C/E-expressing cells but also the percentages of IL-4-, IL-5-, and IL-17-producing cells in TLR3⁺ NK cells increased significantly after infection (P < 0.05). Moreover, the expression of NKG2A/C/E, NKG2D, MHC II, and CD69 on the surface of splenic NK cells was changed in S. japonicum-infected TLR3^-/- (TLR3 KO mice, P < 0.05); the abilities of NK cells in IL-4, IL-5, and IL-17 secretion were decreased too (P < 0.05). These results indicate that TLR3 is the primary molecule which modulates the activation and function of NK cells during the course of S. japonicum infection in C57BL/6 mice.

Differential pulmonic NK and NKT cell responses in Schistosoma japonicum-infected mice

Natural killer cells (NK cells) and natural killer T cells (NKT cells) play a role in anti-infection, anti-tumor, transplantation immunity, and autoimmune regulation. However, the role of NK and NKT cells during Schistosoma japonicum (S. japonicum) infection has not been widely reported, especially regarding lung infections. The aim of this study was to research the NK and NKT cell response to S. japonicum infection in the lungs of mice. Using immunofluorescent histological analysis, NK and NKT cells were found near pulmonary granulomas. Moreover, flow cytometry revealed that the percentage and number of pulmonic NK cells in S. japonicum-infected mice were significantly increased (P < 0.05). However, the percentage and cell number of NKT cells were decreased compared to those of normal mice (P < 0.05). The expression of CD69 on pulmonic NK and NKT cells was increased after infection (P < 0.05), and CD25 expression increased only on NKT cells (P < 0.05). Intracellular cytokine staining showed a higher percentage of IFN-γ⁺ and lower percentage of IL-5⁺ pulmonic NK cells (P < 0.05) compared to controls. However, the percentage of IL-17⁺, IL-10⁺, and IL-5⁺ pulmonic NKT cells significantly increased (P < 0.05). Additionally, there was a significant decrease in NKG2A/C/E (CD94) expression and an increase of NKG2D (CD314) expression on pulmonic NKT cells (P < 0.05), which might serve as a mechanism for NKT cell activation during S. japonicum infection.