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Cells Can Suppress Immune Reaction
Lymphozytes recognise extraneous
tissue and reject transplanted
organs; © NCI Visuals Online
In blood of leukaemia patients, predominantly immature white blood cells can be found. These cells displace the healthy cells and, thus, suppress a normal haematopoiesis. Chemotherapy destroys the diseased cells of the patient which then often have to be replaced by a bone marrow graft.
However, the researchers say, in 30 to 50 percent of the patients, the aggressive immune cells contaminating the bone marrow graft direct themselves against the recipient. This often lethal defence reaction is called 'Graft versus Host Disease' (GvHD). Yet, with the help of regulatory T cells from the blood of the donor, the rejection reaction might be suppressed.
Regulatory T cells or Tregs control aggressive immune cells and, thus, unwanted immune reactions by the graft can be avoided. However, to date, there were no adequate techniques available to securely isolate the regulatory T cells.
Since, in humans, the cell surface marker (CD25) used for the isolation before is also found on the aggressive immune cells, it was hardly possible to clearly separate the helpful Tregs from the dangerous cells. Now, researchers have developed a simple method to specifically isolate these cells from human blood.
With other markers (CD49d and CD127), the scientists now succeeded in separating the aggressive and dangerous immune cells from the helpful, regulatory cells. Thus, it is now possible to isolate regulatory T cells in high purity safely from human blood. Using these T cells, the researchers could already suppress a particular severe form of the 'Graft versus Host Disease' in mice. In a first clinical trial in Singapore, the researchers now want to apply the regulatory cells in leukaemia patients who developed the severe immune reaction after a bone marrow donation.
MEDICA.de; Source: Max-Delbrück-Centrum für Molekulare Medizin (MDC)