ABSTRACT
Early studies of graft-vs.-host reaction (GVHR) quickly identified intestinal damage as an
important component of host disease (1). Most animals with severe GVHR developed
diarrhea, and this feature remains one of the characteristic signs of graft-vs.-host disease
(GVHD) both in humans and in experimental animals. Nevertheless, the mechanisms
responsible for intestinal damage have not been clearly identified. Partly this reflects a fail-
ure to discriminate between intestinal alterations that are true consequences of GVHR and
those that are artefacts of irradiation or infection. Furthermore, the mucosal features vary
markedly with time, even within a single experimental model, and many studies have
failed to appreciate that the intestinal changes present in moribund patients or animals
may not necessarily be relevant to the condition as a whole. Finally, the intestine is a dis-
tinct component of the host immune response, and therefore measurements of systemic
immune responsiveness in animals with GVHR may not reflect events within the intestine.
This chapter will review the intestinal pathology that characterizes GVHD in experimental
animals and under clinical conditions and discuss the possible mechanisms involved.
