Overview

Graft-versus-host disease(GVHD) is one of the classical complications of allogeneic stem celltransplantation. It is dependent on the presence of histocompatibilitydifferences between the host and the donor. These can be minor antigens inthe case of matched transplantation or major histocompatibility complex(MHC) antigens if there is some human leukocyte antigen (HLA)incompatibility. Minor antigens are presented to the T cells presumably inthe same way that bacterial or viral antigens are presented. Thus, inessence, the graft is functioning as if there were a severe infection, andthe graft tries to eradicate antigens that are intrinsic to the host. Thisresults in the tissue damage that we clinically recognize as GVHD.

There are two main categoriesof GVHD, acute and chronic, each with two subcategories:

Acute GVHD

Chronic GVHD

Previously, acute GVHD (aGVHD)was arbitrarily assigned to all allogeneic manifestations that occurredbefore day 100, and cGVHD to those occurring at er day 100, but thisdistinction is no longer considered useful. It is now recognized that therecan be late-onset aGVHD (frequently but not exclusively afterreduced-intensity transplantation), and manifestations of cGVHD may occurbefore day 100.