 Graft-versus-host disease GVHD is a serious complication after bone marrow transplantation from another donor. GVHD is caused by certain cells called lymphocytes. Normally these cells make immune reactions that help protect the body from foreign substances that cause infection. Here, these cells attack the normal tissues of the body as if they were foreign substances. This interferes with the normal function of vital organs and results in their damage. In GVHD these cells attack the skin, liver and bowel. GVHD also increases the chances of infection. 