 |  |  | | | UNIQUE CELL CREATE WORKING THYMUS | | | | |
| |  Thymus
Release Date: 19th June 2002
Researchers at the Centre for Genome Research (University of Edinburgh) have identified a unique stem cell type in mice that can produce a working thymus - a vital immune organ that makes infection-fighting white blood cells (T-cells).
The discovery has implications for the development of new treatments: the stem cells in people could have the ability to help generate patient-specific supplies of T-cells in the laboratory for use in a range of clinical situations including improving the outcome for bone marrow transplant (BMT) recipients.
Reporting in this month's edition of Immunity, the team led by Leukaemia Research Fund researcher Dr. Clare Blackburn, has shown that a discrete group of mouse embryonic cells (thymic epithelial progenitor cells), when implanted into mice lacking a thymus, can restore key T-cell populations. These mature immune cells can only arise by the action of a functioning thymus on bone marrow cells (see notes for editors).
The team must now look to see whether they can find the same cells in humans.
"We have provided working evidence that a unique stem cell is responsible for creating the thymus, the lynchpin in the body's immune system," says Dr Blackburn.
"Evidence suggests that the human thymus will develop in the same way as in mice, but we need to find the specific markers that define these unique cells in humans before we know for sure," she adds.
She believes their work could potentially have an impact on bone marrow transplantation. By isolating these unique cells, they could generate large numbers of customised T-cells in the laboratory, which would impact significantly on the clinical outcome of donor bone marrow transplants.
Before leukaemia and lymphoma patients undergo transplant, they are given intensive radiotherapy which destroys most of the cancer cells but also their immune system. This means they are at considerable risk of infection until the donor's cells help to rebuild the patients immune system over a period of several months.
Transplants carry a number of risks for the patient. One such problem is graft versus host disease (GvHD) which occurs when the immune cells from the donor recognise the cells of the patient as foreign and attack them. There is however a beneficial aspect to GvHD as the donor's immune cells can destroy any residual leukaemia cells that remain (graft versus leukaemia).
If doctors can use these 'thymic stem cells' to educate the T-cells in the laboratory, they may be able to maximise the graft versus leukaemia effect, with the minimum of GvHD.
Scientific Director of the Leukaemia Research Fund, Dr David Grant, says: "This is a really exciting scientific discovery which has a number of implications. Importantly, it presents the possibility that scientists could create an assembly line for generating patient specific immune cells."
This work is supported by the Leukaemia Research Fund (LRF), The Wellcome Trust and the Medical Research Council.
 | Notes for Editors |
 | The thymus is a small organ situated just above the heart. Quite simply, it is a vital part of our immune system. Without it we would not produce white blood cells called T-cells - which have the ability to recognise and attack viruses and infection. After leaving the bone marrow, immature blood cells, or "pre T-cells," are drawn to the thymus. The organ ensures that only those white blood cells with the correct immune response will survive and go out into the blood stream to orchestrate the body's immune response. It does this by helping the cells develop receptors - which allow them to recognise foreign cells that shouldn't be in the body. Importantly it also teaches these T-cells to recognise the body's own tissue so they do not attack it. The newly equipped T -cells are then sent out in to the bloodstream, programmed and ready to fight any viruses or infection that may get in to our body. |
| If the team can isolate the same thymic stem cells in humans, this presents the possibility that the cells could be used to support the creation of T-cells in the laboratory. The cells may also provide vital clues as to how the thymus could be stimulated in people with weak immune systems - including the organ transplant patients and people with immune diseases, including AIDS. They may also be useful in treatments of autoimmune diseases. |
| The Centre for Genome Research is a multidisciplinary research institute focused on the molecular, cellular and developmental biology of stem cells. Its mission is to acquire an understanding of the mechanisms of stem cell self-renewal and differentiation processes. It seeks to provide scientific foundations for the application of cell replacement therapies in the treatment of human disease and injury. |
image?!?!?
This image - provided by Willem van Ewijk - shows T-cells (small round cells) being programmed by epithelial cells (large cells) in the Thymus.
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