Acute GVHD is caused by-
**Core Concept**
Acute Graft-Versus-Host Disease (GVHD) is a major complication of allogeneic hematopoietic stem cell transplantation, where the immune cells from the donor (graft) attack the tissues of the recipient (host). This occurs due to the recognition of the host's tissues as foreign by the donor's immune cells.
**Why the Correct Answer is Right**
The correct answer is due to the activation of donor T lymphocytes, which recognize the host's major histocompatibility complex (MHC) molecules as foreign. This leads to the proliferation and activation of donor T cells, which then release cytokines and chemokines that cause damage to the host's tissues. The activation of donor T cells is mediated by the recognition of the host's MHC molecules by the donor's T cell receptor (TCR), which is a complex of TCR, CD3, and CD4 or CD8 molecules.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not specify the involvement of donor T cells in the pathogenesis of acute GVHD.
**Option B:** This option is incorrect because it does not accurately describe the mechanism of acute GVHD. While donor T cells do play a role in the pathogenesis of acute GVHD, the recognition of host MHC molecules is the primary trigger.
**Option C:** This option is incorrect because it does not specify the type of cells involved in the pathogenesis of acute GVHD. While antibodies and complement do play a role in chronic GVHD, they are not the primary cause of acute GVHD.
**Clinical Pearl / High-Yield Fact**
The incidence and severity of acute GVHD can be reduced by using T cell-depleted grafts, using immunosuppressive medications such as cyclosporine and tacrolimus, and using GVHD prophylaxis regimens that include corticosteroids and other immunosuppressive agents.
**Correct Answer:** C. Donor T cell recognition of host MHC molecules.