After a donor stem cell transplant, there’s a possibility that the new cells (the graft) will react against your own cells (the host).
This reaction is called graft-versus-host disease (GvHD). It happens when the donor immune system attacks your body tissues.
Occasionally, the donor’s stem cells may be treated with antibodies before the transplant. This is to remove white blood cells called T-lymphocytes that doctors think cause GvHD. Removing the T-lymphocytes is usually done if a severe graft-versus-host reaction is possible – for example, if stem cells from an unrelated donor are used.
Graft-versus-host disease doesn’t mean that the transplant has failed. It can even have benefits, as the donor cells may attack any cancer or leukaemia cells that have survived.
The effects of GvHD are usually mild, but in some people they can be severe and even life-threatening. GvHD mainly affects the skin, mouth, stomach, bowel and liver. It may affect one part of the body or several. The first signs can happen up to six months after your transplant.
In the past, GvHD that occurred within 100 days of transplant was called acute GvHD. If it happened more than 100 days after transplant, it was called chronic GvHD. But with reduced-intensity conditioning treatment, acute GvHD can now happen after 100 days as well. A treatment called donor lymphocyte infusions (DLI) can be given after day 100 and can also cause acute GvHD symptoms.