Transplantation Immunobiology Group Projects
An advance in surgical and immunosuppressive techniques has led to organ transplantation as the method of choice for the treatment of many diseases. However, the number of suitable donors is dwindling, due to many factors, but largely because of the reduction in deaths from car accidents. Xenotransplantation, the transplantation of organs from species other than humans, is now seen as a viable solution to the world wide problem of lack of supply of suitable human donors.
The pig is the most suitable animal for a variety of reasons. Unfortunately, all humans contain natural antibodies to pig tissues The antibodies would bind to the transplant and cause its destruction within minutes (so called "hyperacute rejection"). Recent studies from our laboratory have indicated that most, if not all, of these human antibodies react with the sugar galactose that is present on many molecules on the surface of transplanted pig tissues. Our studies have indicated a large amount of galactose is present in pig blood vessels and this guarantees the early rejection of transplanted organs such as kidney, heart and liver. The production of pigs that do not express the galactose sugar is an important pre-requisite for successful xenotransplantation. Mice that lack this sugar were produced and form the basis of our experimental models. However, until the recent use of animal cloning by nuclear transfer the technology to perform this in pigs was not available. We had described an alternative strategy to reduce the amount of galactose sugar expressed by transgenic animals, a technique that is suitable for the production of transgenic pigs. We will examine a number of different transgenic mice expressing a combination of genes that reduce the expression of the galactose sugar and determine the effects of these modifications on organ and cell transplantation. These studies will be the prelude to the production of pigs that could be used for human transplantation.
As galactose is a sugar, the laboratory also studies the enzymes that add sugar to cells. Glycosylation (addition of carbohydrate) of proteins and lipids by the cell has a profound influence on all aspects of the life of the cell and the whole organism. This process occurs in the endoplasmic reticulum and Golgi apparatus where a group of enzymes known as glycosyltransferases, sequentially add sugars. This project aims to study the structure - function relationship of these biologically important enzymes by several means. Genetic engineering techniques will be used to generate mutants of these enzymes so that they are no longer able to transfer the appropriate sugar. Finally, we have shown that these enzymes are specifically located in a subcompartment of the cell due to a small amino acid sequence on part of the glycosyltransferase and we will use the techniques of molecular biology to clone the protein receptors that bind these enzymes. Sugars on the surface of cells of the immune system are also studied. Lymphocytes, also known as white blood cells, are important for the well being of all individuals. They are the cells that fight infection by microorganisms. The lymphocyte gets its information about environment and communicates with other cells using molecules on the cell surface. We are examining a group of molecules found on the surface of different lymphocytes that bind different sugars. These studies will examine the structure of the molecules that interact with sugars in order to understand how these give messages to the lymphocyte that trigger various functions the cells perform in the immune response. We will isolate the genes for these and study their function in detail.
The cell surface carbohydrate receptors represent several different families of molecules and it is highly likely that these have important roles in the immune response. The potential significance of studying these molecules on the lymphocyte cell surface is in defining the functional properties of these molecules. This will give us novel insights into the molecular mechanisms involved in the generation of immune responses and the mechanism of immunodeficiency and autoimmunity.
The broard areas of research include:
- Transplantation Immunobiology
- Modification of graft tissue to express immunomodulatory genes/proteins that will regulate rejection/inflammation locally or induce tolerance
- Dendritic cell biology including cytokine requirements and signalling pathways
- Genetically engineer dendritic cells to express molecules to directly inhibit T cell proliferation, block costimulation or maintain the dendritic cells in a tolerogenic immature form
- Regulatory T cells
- Islet transplantation for Type I diabetes
- Glycoimmunology
- Structure, function and cell biology of glycosyltransferases, particularly Family 6 (containing ABO blood group transferases
- The role of glycolipids in cell activation and apoptosis
- Anti-carbohydrate antibodies, including structure, role in inflammation/graft rejection (chronic)
- Natural autoantibodies including biology, mechanisms of regulation and role in disease
- Carbohydrate receptors of innate immune cell
Projects
top of page- Immunosuppression using expression of immunomodulatory molecules
- Glycobiology of glycosyltransferases relevant to xenotransplantation
- Islet Cell Transplantation