What is the primary etiology of acute graft-versus-host disease (GVHD) following a bone marrow transplant?

Acute graft-versus-host disease (GVHD) primarily arises from an immune response where the donor's lymphocytes attack the host's tissues. This phenomenon occurs after a bone marrow transplant, where the transplanted immune cells recognize the host's tissues as foreign. The activated T cells from the donor graft invade the host's skin, liver, gastrointestinal tract, and other organs, leading to inflammation and tissue damage.

In GVHD, the mismatch of major histocompatibility complex (MHC) molecules between donor and recipient plays a crucial role; the T cells in the transplant are particularly active against the host's antigenic disparities. This immune-mediated attack results in the classic symptoms associated with acute GVHD, which can include skin rash, diarrhea, liver dysfunction, and fevers.

Thus, understanding that the underlying mechanism is the donor's immune response against the host's own cells is key to recognizing the nature of acute GVHD following bone marrow transplantation.