The hematopoietic system is how new blood cells are formed; hematopoietic stem cells in bone marrow generate new, replacement hematopoietic stem cells as well as mature blood cells such as red blood cells and leukocytes. The system is also very sensitive, and cancer can arise there. When diseases like leukemia strike, one treatment option is a bone marrow transplant, known as an allogeneic hematopoietic stem cell transplant. (allogenic trasnplants use donors while autologious procedures use a patient's cells). Over 40,000 of these procedures are carried out every year around the world, and though they can be tremendously helpful, complications can also arise. The recipient's body might reject the donated cells, in which the T cells of the recipient's immune system attack the new cells and cause inflammation.
New research has shown that these T cells can come from the skin, and move through the blood to other organs, such as the intestine, and cause inflammation there too. This study, which was reported in the Journal of Experimental Medicine, could help researchers improve stem cell transplants.
In bone marrow transplants, chemotherapy and radiation is used to eliminate the patient's own stem cells (in their bone marrow) and once gone, they can be replaced with donated, healthy bone marrow and the stem cells it contains. But after these transplants, patients may develop serious inflammatory skin diseases; the bone marrow might be rejected in a condition called graft-versus-host reaction or graft-versus-host disease (GVHD).
Previous work by this group revealed a mechanism underlying GVHD. In this study, the researchers used skin samples from transplant patients that were taken before and after the procedure to show that T cells that come from the transplant recipient can cause the skin inflammation. T cells that are considered skin residents were also identified in the blood of transplant recipients. The researchers "found an astonishing number of cells that originally came from the skin” in the intestines of transplant recipients.
The scientists are interested in deactivating these T cells in transplant patients. It also may be possible to use these circulating T cells as a biomarker that could indicate when patients are at risk for serious complications after a bone marrow transplant. Instead of taking a skin biopsy from patients with inflammatory disorders in the skin, a liquid biopsy using blood may be a less invasive alternative.