Research overview
Human diseases: rheumatoid arthritis (RA), multiple sclerosis (MS)
There are a number of diseases, called "autoimmune", in which specific tissues are attacked by an immune mediated destructive and chronic inflammation without any evidence for infection or allergy. There are several of our most important diseases in this group such as rheumatoid arthritis (RA), multiple sclerosis (MS), type I diabetes, Sjögren syndrome (SS) and systemic lupus erythematosus (SLE). In spite of enormous research efforts resulting in a large number of publications we know in fact very little about the cause of the diseases. We do not know if they are autoimmune, we do not know which genes predispose for disease or which environmental factors that triggers them and more importantly, there are no current effective treatments that can reverse the disease course. We strongly believe that we need to take one step back to take two steps forward. We need to understand the pathogenic events that lead to the chronic development of tissue destruction in these diseases. And this is best done using animal models in which such basic questions can be addressed.
Characteristics of "autoimmune" inflammatory conditions such as RA and MS:
> They are syndromes caused by many different pathways;
> They are inflammatory states affecting primarily specific tissues with limited exposure to the immune system;
> They are chronic;
> They are dependent on a clear genetic influence (10-50% concordance in MZ studies), and the genetic influence is to a significant degree associated with genes in the major histocompatibility complex (MHC).
> They are inflammatory states affecting primarily specific tissues with limited exposure to the immune system;
> They are chronic;
> They are dependent on a clear genetic influence (10-50% concordance in MZ studies), and the genetic influence is to a significant degree associated with genes in the major histocompatibility complex (MHC).
Genetics of RA and MS
The disease manifestations in RA and MS are very complex and it is easy to document activity of most pathways, cytokines, receptors or cells that one might be interested. This does not however directly address the pathogenic disease mechanisms. There must be a number of crucial events, determine by genes and environmental factors that promote the development of an otherwise normal process into pathology. In fact, there are high expectations from scientists and the public that we should be able to identify such genes through the recent advancement of genome research and also expectations from politicians that we could understand the diseases through epidemiological scans of environmental factors. The problem is that these diseases are quite complex, not only in their pathogenesis, but also in their genetic control and the influence by environmental factors.
Obstacles in defining genes causing a complex disease such as RA and MS:
* Genetic heterogeneity. The same disease could be caused by different sets of genes in different individuals;
* Polygenicity – controlled by many genes. Many of these penetrate only upon interaction;
* Complexity – influence by environmental and stochastic factors.
However, we think there is a way out. This is to combine genetics with animal models in which specific pathogenic pathways can be studied. Not only genetics has been better but also animal models. It is today possible to more precisely study specific pathways leading to autoimmune disease in animal models. These pathways are evolutionary conserved and the fact that diseases develop, or can be induced, in animals leads to disease that mimic the human counterpart shows that such pathways can result in similar type of disease. Animals offer new possibilities since they are inbred, they can be bred systematically with short generation times and they can be manipulated genetically and also with induction of disease.
Animal models
In the laboratory we are trying to improve the animal models for different autoimmune disease. This will lead to more efficient progress in research to understand the human disease and will thereby also reduce the animal suffering. We have made significant contribution to this and introduced more appropriate models and ways to induce them for both RA and MS.
It is also important to have many different models for these disease since both RA and MS is most liklely consisting of many different disease; each of which may be represented by different animal models.
Animal models for inflammatory diseases in the MIR laboratory:
| Disease |
Model |
| Rheumatoid arthritis | – Collagen induced arthritis (CIA) in mice and rats; – Pristane induced arthritis (PIA) in rats; – Cartilage oligomeric matrix protein induced arthritis (COMPIA); – Autologous type XI collagen induced arthritis (CXIIA); – Anti-CII antibody induced arthritis (CAIA). |
| Multiple sclerosis | – Chronic relapsing experimental allergic encephalomyelitis (EAE) in mice and rats. |
| Spondyloarthropathis | – Stress induced enthesiopathy (SIA). |
| Sjögren´s syndrome | – Spontaneously occuring in selected mouse strains. |
| Relapsing polychondritis | – Matriline-1 induced relapsing polychondritis (MIRP). |
| Systemic lupus erythematosus | – Spontaneously occuring in selected mouse strains. |
| Type I diabetes | – Spontaneously occuring in selected mouse strains. |
Our main goals are:
1) To identify the most important genes that control relevant animal models for rheumatoid arthritis and multiple sclerosis. In particular we aim to understand the genes determining the pathogenic events transforming the disease into chronicity.
2) To understand the role of MHC class II genes in explaining the immune specificity of autoimmune disease.
3) To use the animal models not only for understanding the basic mechanism of autoimmune disease but also as models for developing new diagnostic, preventive and therapeutic strategies for autoimmune diseases such as rheumatoid arthritis and multiple sclerosis.
Genetic studies in animal models
We search for genes controlling disease and specific disease pathways by analysing gene segregating crosses between resistant and susceptible strains. By genotyping the offsprings we try to identify the most important gene regions associated with disease. Subsequently, we can isolate these gene regions in so called congenic strains. The congenic strains can be used to understand the biological role of the genes and also identify the responsible gene or genes in these regions.
We have so far identified genetically inbred strains that differ in susceptibility to many of the animal models for RA and mS and other disease and have identified the genetic regions that harbour the polymorphic genes of interest. We believe that these genes will be of critical importance to understand the critical pathogenic events in the disease. It should however be emphasised that it has not yet been possible to identify such a gene in any autoimmune complex disorder, possibly except MHC class II as discussed below. The animal models do, however, provide excellent possibilities for such studies and it is a question of time when these genes will bed unravelled. It will however be quite complicated to understand how they interact and their exact role in the pathogenesis. Many projects in our laboratory aim to identify these genes and understand how they work, For these studies we use a series of congenic strains in both mice and rats controlling different pathways leading to disease. We are trying to isolate genes by positional cloning and comparative mapping technology and the diferent pathways studied with identification of differentially expressed genes using microarray technology.
The major histocompatibility complex region: the role of T and B cells
Most autoimmune diseases are associated with the MHC region, in RA and MS with the class II region of MHC. However, it has not been possible to identify the responsible genes and its not clear how thye affect the disease process. Very challenging data has been accumulated in RA in which it has been shown that most DR alleles that are associated with disease share a particular sequence in the peptide binding region of the class II molecule. This is a strong argument for a role of the class II gene and for a role of immune specificity in the disease.
Also in most animal models for RA it has been possible to identify the MHC region to be important. In one of these models, in collagen induced arthritis in the mouse, we were able to produce conclusive evidence of the MHC class II Abq gene to be important. We also know considerable details on recognition structures but do still not know exactly how it is operating for disease development. We have also shown that this gene product is strikingly similar to the DR molecule postulated to play a role in RA and shown that the expression of the human DR4 gene in the mouse in fact also predispose for the same type of collagen induced arthritis. We have obtained similar findings using models for MS. Thus, it is possible to identify genes in the animal model and it is possible to humanise the mice and it will most likely be possible in the future to understand its function. Of particular relevance will be to understand its function together with other genes of importance for the disease.
The MHC class II molecules are cell membrane peptide receptors – the peptides are the antigen recognized by T cells. This interaction is a critical step in antigen-specific T cell activation and is possibly a critical step also in the development of autoimmune diseases. We have identified the peptides bound to the Aq molecule, the CII256-270 peptide derived from the type II collagen molecule and we know that the major recognition structure is a carbohydrate bound to lysine at position 264. T cell recognition of this structure is bottleneck for development of CIA. We also know that T cells normally recognize this structure in vivo. After interaction they can be deleted, or tolerized, thus normally preventing development of arthritis. However, when the mice are immunized with CII these T cells seem to be possible to activate to a state when they can start a process leading to arthritis. Many projects in the lab aim understand how this occurs and in these projects we use mice that are transgenic or mutated in T cell receptors, type II collagen and MHC.
One important step towards arthritis is the activation of B cells. B cells can be activated to produce antibodies to CII but requires help from CII reactive T cells. These B cells produce antibodies that can directly cause arthritis through binding to the cartilage surface and initiating complement and Fc-receptor dependent inflammatory cascades. There are projects in the laboratory aiming to understand which structures are recognized by these arthritogenic antibodies, how B-cells are regulated, if B cell can present CII to T ell through their own class II molecules and how the antibody attack on cartilage is mediated and controlled. For these studies we are using mice genetically mutated in the specific epitopes on CII and mice with various defects in B cells and MHC molecules. Similar projects on MHC, the role of T and B cells and their activation are also ongoing in models for MS.
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Medical Inflammation Research (MIR) 