A dose of ultraviolet (UV) radiation staves off graft vs. host disease (GVHD) after a bone marrow transplant, report Miriam Merad and colleagues in the May issue of Nature Medicine. In mice, UV treatment kills Langerhans cells, immune cells in the skin that can prompt the disease.
GVHD is caused when T cells derived from the transplant attack the skin, liver, gut and other tissues in the patient. But these T cells don't do it alone. They are helped by cells in the patient, including Langerhans cells. Merad and colleagues found that after transplantation, Langerhans cells can linger in the skin, providing a trigger for T cells and for GVHD. The investigators then found that if they eliminated Langerhans cells with UV radiation, they could help prevent GVHD in the skin, the most commonly affected organ in GVHD. Mice zapped with UV light, that were undergoing transplants, fared much better than mice that did not receive UV treatment. No one knows exactly why UV radiation kills Langerhans cells; but the treatment did not appear to affect the rest of the skin.
The results dovetail with other work suggesting that ultraviolet light can improve GVHD-induced lesions in the skin of human patients, and could mark the first step to tanning booths in the transplant setting. GVHD afflicts 30 to 50 percent of all transplant recipients.
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