Existence of LysRS-MITF/Hint1 pathway in dendritic cells (IRM12P.642)

Using murine bone marrow derived dendritic cell line JAWS II, we investigated the existence of LysRS-MITF/Hint1 pathway in dendritic cells (DC). Based on florescence microscopy, unstimulated cells expressed LysRS predominantly in the cytoplasm. LysRS localization was increased in the nuclei 2 h after stimulation with LPS, RANKL, GM-CSF (LRG) and was sustained over 6 h. To examine its functional role, doxycycline (Dox)-controlled plasmid overexpressing a single point mutant of LysRS (Ser207 to Asp) that mimics constitutive phosphorylation (LysRSS207D) was stably transfected into the JAWS II cell line. Dox-treated LysRSS207D cells were more dynamic, showed increased cell spreading and motility compared to wild-type cells and to untreated LysRSS207D cells. Moreover, Dox-treated LysRSS207D cells exhibited up-regulation of MHCII, but not CD11c, CD80, CD86 and CD40. Primary cultures of bone marrow derived dendritic cells (BMDCs) from C57BL/6 mice were also examined. Bone marrow cells transfected with NUDT2 siRNA inhibited development into BMDCs compared to scrambled siRNA control. Taken together, LysRS-MITF/Hint1 pathway exists in DC and appears to play an important role in DC morphology, maturation and development. Next steps include measurement of cytokine levels, primary allogeneic T cell activation, and adoptive transfer in our asthma and flu models.

Expression of CD40L on CD8 T cells and its role in influenza A infection (IRC5P.618)

CD8 T cells play an important role in protective immunity against a wide range of pathogens and the factors that control their activation are clearly important. CD40L-mediated CD40 licensing of dendritic cells by CD4 T cells is known to be necessary for the generation of a robust CD8 T cell response. Less clear is the contribution of CD40L on CD8 T cells to their activation. We have previously shown that CD8 T cells are able to induce the production of IL-12 p70 by dendritic cells in a CD40L-dependent manner. To better understand the role of CD40L on CD8 T cells responses, we generated and characterized CD40L-expressing CD8 T cells both in vitro and in vivo. We found that CD40L is expressed on 30-50% of activated effector CD8 T cells and the differentiation of CD8 T cells into CD40L-expressing cells is strongly induced by IL-12, suggesting the presence of a positive feedback mechanism mediated by CD40L and IL-12. Using an influenza A mouse model, we examined whether this mechanism is involved in the primary expansion of CD8 T cells during an infection and whether CD40L-expressing CD8 T cells are able to license dendritic cells for optimal memory CD8 T cell programming. In the absence of CD40L signaling, the ability to upregulate CD25 and downregulate CD62L is diminished in CD8 T cells, causing an impairment in their primary expansion and also their ability to accumulate at the site of infection.

Existing allergic inflammation alleviates influenza infection (HYP5P.319)

Asthma is a disease suffered by millions throughout the world and its prevalence continues to increase. During the 2009 influenza pandemic asthma was found to be the commonest comorbid illness of patients admitted to hospital. It was also observed that asthmatics admitted to hospital with influenza infection were less likely to die or require admission to intensive care compared with non-asthmatics. Using an in vivo model of asthma and influenza infection we demonstrate that prior exposure to Blomia tropicalis extract (BtE) led to a reduction in weight loss and faster recovery following influenza infection compared to PBS/influenza infected mice. This was accompanied by an earlier increase in both CD4 and CD8 T cells in the lungs, which produced more INF-γ, TNF-α and expressed higher levels of CD107a at day 8 post infection. At day 14 post infection levels of T cells in the lungs of the BtE/influenza group were significantly reduced, which parallels the faster recovery from weight loss seen in this group. In summary, we have shown that prior exposure to BtE leads to an altered immune response to influenza infection, comprised of less severe weight loss and the faster recruitment of more highly activated T cells in to the lungs. The earlier recruitment of T cells led to faster resolution of disease and a reduction in T cell numbers. We believe this data provides a clue as to why asthmatic patients present with less severe disease when infected with influenza.

Severe asthma, airway re-modelling and induced bronchial associated lymphoid tissue produced using novel dust mite specific CD4 T cell receptor transgenic mice (HYP2P.327)

Patients with severe asthma are very difficult to manage are present a major medical challenge. Development of clinical asthma requires many years of patient exposure to allergens. Mouse asthma models require weeks and are normally transitory and do not lead to allergen-induced dyspnea. We have followed an alternative approach to conventional immunization through the transfer highly polarized CD4 T cell receptor transgenic T cells specific for the dust mite allergen Blo t 5 followed by thrice weekly intranasal recombinant challenge with recombinant allergen to induce persistent high levels of eosinophilia (4 million/mouse lavage) and serum IgE (40,000 ng/ml) and specific IgG1 (30,000 ng/ml). Intranasal challenge of these mice with 25ug of allergen is well tolerated, but a fourfold increase to 100ug induces respiratory symptoms within 15 minutes. These mice show evidence of mucus plugging, increased collagen deposition, mucus hypersecretion and the formation of bronchial associated lymphoid structures (iBALT). Neutralization of IL-4 or IL-13 with monoclonal antibody reduced the response and a combination of these two was most effective. Many drugs reduce respiratory inflammation in mice yet fail to benefit asthmatic patients. We hope that the model described here may help identify new/better drugs for the treatment of patients with severe asthma.

Antigen-specific effector CD8 T-cells inhibit allergic responses via IFN-gamma secretion and dendritic cell interaction (103.4)

Allergic inflammation of the airways causes changes in the lung wall that lead to inflammatory diseases such as asthma. Using a mouse model this response can be divided into an induction phase and an effector phase. Previously we have shown that transfer of CD8 T cells inhibits the induction of Th2 responses. In this study we have investigated the effect of CD8 T cells on the effector phase of the inflammatory lung response. In vitro activated OT-I CD8 T cells were transferred to ovalbumin (OVA)-alum immunized mice one day before challenge with OVA. Eosinophil infiltration and mucus secretion were inhibited by transfer of CD8 T cells. When OT-IxIFN-gamma-/-T cells were transferred, the inhibitory effect was abolished, suggesting an important role for IFN-gamma. In fact, without IFN-gamma, effector CD8 T cells were able to induce asthma-like inflammation which further proved the importance of IFN-gamma in the suppression of type II inflammation. We also investigated the effect of CD8 T cells on lung dendritic cell (DC) function. CD11c+CD11b+CD103- DCs from CD8 transferred mice increased largely in number and when co-cultured with CD4 T cells, they were able to induce more IFN-gamma production. These results suggest that in addition to regulating the induction of the allergic immune response, CD8 T cells can subsequently divert the local lung environment to one that favors Th1 immunity, through IFN-gamma and CD8-DC interaction.

Human CD8 T cells drive Th1 responses through differentiation of TNF/iNOS-producing dendritic cells (147.4)

TNF/iNOS-producing (Tip) dendritic cells have been shown to arise during inflammation and are important mediators of immune defense. However, it is still relatively unclear which cell types contribute to their differentiation. Here we show that CD8 T-cells, through the interaction with DCs, can induce the rapid development of human monocytes into Tip-DCs which express high levels of TNF-α and iNOS. These cells exhibited T-cell priming ability, expressed high levels of MHC class II, up-regulated co-stimulatory molecules CD40, CD80, CD86, toll-like receptors TLR2, TLR3, TLR4, chemokine receptors CCR1 and CX3CR1 and expressed the classical mature DC marker, CD83. Differentiation of monocytes into Tip-DCs was partially dependent on IFN-γ as blocking the IFN-γ receptor on monocytes resulted in a significant decrease in CD40, CD83 expression and TNF-α production. Importantly, these Tip-DCs were capable of further driving Th1 responses by priming naive CD4 T-cells for proliferation and IFN-γ production and this was partially dependent on Tip-DC’s production of TNF-α and NO. Our study hence identifies a role for CD8 T-cells in orchestrating Th1-mediating signals through the differentiation of monocytes into Th1-inducing Tip-DCs.

Interferon gamma limits the magnitude of CD8 T cell responses in the lung during influenza infection (49.24)

In response to a viral challenge, antigen specific CD8 T cells proliferate and gain effector functions while simultaneously acquiring the capacity to secrete cytokines such as interferon gamma (IFN-γ). IFN-γ is thought to play a role in the homeostatic control of antigen specific CD8 T cell numbers although the mechanism by which this occurs is still unclear. Infection of mice deficient for IFN-γ (IFN-γ-/-) with PR/8 influenza was associated with increased antigen-specific CD8 T cell counts in the lung and the BAL fluid when compared to wildtype (WT) C57BL/6 mice. Using in vitro experiments, we show that there is no difference in the rates of proliferation of the WT and IFN-γ-/- CD8 T cells. However upon stimulation, we observed increased cell death in WT CD8 T cells compared to their IFN-γ-/- counterparts. This effect could be reversed upon addition of IFN-γ to the IFN-γ-/- CD8 T cells in a dose-dependent manner. We also observed decreased cell death in the WT CD8 T cells after blocking IFN-γ signaling. These experiments suggest that increased antigen specific CD8 T cell counts in IFN-γ-/- mice is not the result of increased proliferative capacity but is instead due to the absence of IFN-γ-induced CD8 T cell death. Our results suggest that IFN-γ plays a role in promoting cell death that limits the CD8 T cell response during an influenza viral infection.