Acute and chronic graft-versus-host disease.

Acute graft-versus-host disease is a two-step process. First, allorecognition of histocompatibility antigen activates T lymphocytes, which releases several cytokines, including interleukin-1 and tumor necrosis factor. Understanding of this activity resulted in new therapeutic approaches. Chronic graft-versus-host disease remains a very frequent and difficult problem to treat. Thalidomide was introduced as therapy for chronic graft-versus-host disease. Although basic research reported this year had no common theme, progress was made in many areas.