Absence Of CC Chemokine Receptor 6 Dysregulates The Humoral Immune Response.
Funder
National Health and Medical Research Council
Funding Amount
$524,820.00
Summary
The individual steps leading to the activation and differentiation of B cells and the formation of mature functional germinal centres have been investigated in detail and are well understood. In contrast, the underlying molecular signals, which regulate the different events and prevent either autoimmunity or immunodeficiency are still not fully comprehended. This proposal will address these regulatory steps that prevent autoimmunity.
Cells of the immune system need to recognise characteristic viral and bacterial molecules, in order to identify infection. Some immune cells can detect the presence of viral and bacterial DNA. The cells respond by making a number of anti-viral or anti-bacterial molecules, as well as activating other cells to fight the infection. The effect of bacterial DNA can be mimicked by certain short synthetic pieces of DNA. The potent activity of this synthetic DNA (termed CpG DNA ) is being exploited in a ....Cells of the immune system need to recognise characteristic viral and bacterial molecules, in order to identify infection. Some immune cells can detect the presence of viral and bacterial DNA. The cells respond by making a number of anti-viral or anti-bacterial molecules, as well as activating other cells to fight the infection. The effect of bacterial DNA can be mimicked by certain short synthetic pieces of DNA. The potent activity of this synthetic DNA (termed CpG DNA ) is being exploited in a number of clinical trials for treatment of cancer and allergy, as well as to improve vaccinations. Despite the rapid advance towards clinical application, there is still much basic information to learn about how CpG DNA acts on cells. The molecule to which DNA binds in order to activate the cells is called TLR9. TLR9 is not on the surface of cells, but within cells. In a bacterial infection, cells called macrophages engulf and digest bacteria and release the bacterial DNA within the cell, where it binds to TLR9. In other cases, including when CpG DNA is used therapeutically, the DNA needs to be taken up into the cell. Evidence shows that there is a receptor on the cell surface which binds DNA, and takes it into the cell. In this project we propose to identify this DNA uptake receptor. Apart from the use of CpG DNA, there are a number of other proposals for the therapeutic use of DNA. Although it is known that DNA enters into cells, the route for this has not been established. Whilst CpG DNA can activate immune cells, some other distinct DNA molecules can prevent the activation. We will examine whether these inhibitory DNA molecules bind more effectively to TLR9 than the CpG DNA, but do not activate the cell. These inhibitory molecules are proposed as a therapy for the autoimmune disease lupus, which involves inappropriate responses to DNA, and is thought to involve TLR9. In order to develop therapies, a detailed knowledge of how they work is essential.Read moreRead less
Cellular Activation And Apoptosis In Response To Foreign Cytoplasmic DNA
Funder
National Health and Medical Research Council
Funding Amount
$496,446.00
Summary
Viruses are simple organisms. They grow within cells, needing host cell proteins for their replication. Viruses have only a few proteins of their own, and evolve rapidly to change these. It is therefore challenging for the immune system to identify viral infections. Recently it has been recognised that the genetic material of viruses (DNA or RNA) is detected by the immune system. A novel pathway for recognition of viral double stranded DNA is emerging. The genetic material of mammalian cells (DN ....Viruses are simple organisms. They grow within cells, needing host cell proteins for their replication. Viruses have only a few proteins of their own, and evolve rapidly to change these. It is therefore challenging for the immune system to identify viral infections. Recently it has been recognised that the genetic material of viruses (DNA or RNA) is detected by the immune system. A novel pathway for recognition of viral double stranded DNA is emerging. The genetic material of mammalian cells (DNA) is found within the membrane-bound nucleus of the cell. The presence of DNA outside the nucleus in the cytoplasm is abnormal, and is detected as an indication of viral infection. This causes either death of the cell, or activation to produce anti-viral molecules. We have identified a protein from the cytoplasm of cells which binds specifically to DNA. This protein, X is found in association with foreign DNA within 5 minutes of it being introduced into the cell. In this project we propose to confirm that X recognises foreign DNA and initiates cellular activation or death. Other molecules to which X binds during this process will be identified. This project is relevant to a number of problems in health and disease as well as biotechnology. In both gene therapy and biotechnology, DNA is introduced into cells in order to allow those cells to make specific proteins. The cell sees the introduced DNA as a potential viral infection, and it responds in ways which limit the production of the desired proteins. Lupus is an autoimmune disease with high levels of DNA in circulation. X is proposed as a protein involved lupus in mouse models. We suggest that DNA taken up by cells is recognised by X and this contributes to the disease. Understanding the means by which DNA is recognised in the cytoplasm may allow the development of much more efficient processes for gene therapy and protein production in biotechnology, and more effective lupus and antiviral therapies.Read moreRead less
Defining The Immunoregulatory Function Of Roqin: A Novel Gene Essential For Preventing Autoimmunity
Funder
National Health and Medical Research Council
Funding Amount
$721,250.00
Summary
Lupus is a systemic autoimmune disease that carries significant morbidity and mortality. Virtually any organ can be affected, including kidneys, brain and blood. Lupus is the result of a breakdown in normal regulation of the immune system. Although there is clearly a significant genetic contribution to lupus, few causative genes have been found in humans with this disease. Recently, we discovered a novel mutation in a new gene (named roqin), that cases lupus in mice. Based on preliminary investi ....Lupus is a systemic autoimmune disease that carries significant morbidity and mortality. Virtually any organ can be affected, including kidneys, brain and blood. Lupus is the result of a breakdown in normal regulation of the immune system. Although there is clearly a significant genetic contribution to lupus, few causative genes have been found in humans with this disease. Recently, we discovered a novel mutation in a new gene (named roqin), that cases lupus in mice. Based on preliminary investigations and prediction based on the structure of Roqin, we suspect that this gene may be a key immune regulator. Specifically, it is likely to be involved in maintenance of immunological self-tolerance, which normally prevents development of autoimmunity. Mice carrying the Roqin mutation have an abnormality of their T cells, which causes them to be abnormally activated, divide more readily and survive for longer. Hyperactivated T cells induce B cells to proliferate and secrete antibodies against self-tissues that eventually lead to loss of platelets, kidney damage, enlarged spleen and lymph nodes, and early death. We now want to investigate precisely how Roqin causes abnormal T cell activation. The protein sequence of Roqin predicts the existence of two zinc finger domains that are highly conserved across species and play critical functions in regulating cell growth. One of the zinc fingers is a RING domain known to have a ubiquitin-ligase activity, which is known to play a crucial role in negative regulation of lymphocyte signalling, and maintenance of tolerance. The other zinc finger domain is known to be important for destabilizing mRNA of cytokines, thereby influencing communication between lymphocytes. Elucidation of this novel mechanism of disease will help understand the cause of human lupus. It will also provide clues about more specific drug therapies that might be more efficacious, and carry less toxicity than those currently available.Read moreRead less
Follicular T Helper Cells: Critical Regulators Of Humoral Immune Responses
Funder
National Health and Medical Research Council
Funding Amount
$272,591.00
Summary
B cells are important cells of the immune system that are responsible for producing antibodies in response to infection with pathogens, such as bacteria or viruses, or following vaccinations. In order for B cells to accomplish this task, they require help from a specialised popualtion of T cells, which are another type of immune cell - these are known as follicular T helper (TFH) cells. Under normal circumstances, T cells and B cells specifically interact with one another within lymphoid tissues ....B cells are important cells of the immune system that are responsible for producing antibodies in response to infection with pathogens, such as bacteria or viruses, or following vaccinations. In order for B cells to accomplish this task, they require help from a specialised popualtion of T cells, which are another type of immune cell - these are known as follicular T helper (TFH) cells. Under normal circumstances, T cells and B cells specifically interact with one another within lymphoid tissues such as tonsils, spleens and lymph nodes - here, they engage in a dialogue, the end result of which is the B cells being instructed to produce the appropriate type of antibodies by T cells. However, if tis process is not regulated, the T cells can deliver too little of too much help - this can result in several different types of diseases of the immune system, such as immunodeficiencies (ie insufficient production of antibodies, resulting in individuals becoming susceptible to infections) or autoimmunity (ie production of inappropriate types of antibodies that can recognise cells of the host, resulting in tissue damage and organ failure). The means by which TFH cells instruct B cells to produce antibodies is not completely understood. This project will seek to determine the mechanism whereby TFH cells carry out this important function by performing detailed examination of them follwoing their removal from tissues such as human tonsils and spleens. In doing so, we hope to design approaches that will allow the function of TFH cells to be improved in cases of immunodeficiencies, or suppressed in situations of autoimmune diseases.Read moreRead less