Graft rejection and graft-versus-host disease: mirror images.

Graft rejection and graft-versus-host disease (GvHD) complicate bone marrow transplantation in animals and man. The likelihood of each correlates with the degree of genetic disparity between donor and recipient. However, instead of a direct relation between graft rejection and GvHD, these events are inversely correlated: in most instances, they are mutually exclusive. A similar, complex relation exists with a third possible event, graft-versus-leukaemia. Attempts to suppress graft rejection or GvHD are likely to increase the reciprocal outcomes unless additional measures are instituted.