Which of the following factors is the most likely to increase the risk of graft vs host disease (GHVD)?

• A. Matching white blood cell antigens between two siblings.
• B. An autograft by the patient.
• C. A significant difference in human leukocyte antigens between the recipient and donor.
• D. The donor and recipient are not directly related.

Answer: (C)

Verified step by step guidance

1. Step 1: Understand what Graft Versus Host Disease (GVHD) is — it is a condition where the donated immune cells (graft) attack the recipient's body (host) after a transplant, typically seen in bone marrow or stem cell transplants.
2. Step 2: Recognize the role of Human Leukocyte Antigens (HLAs) — these are proteins on the surface of white blood cells that help the immune system distinguish self from non-self. Matching HLAs between donor and recipient reduces the risk of GVHD.
3. Step 3: Analyze the options given: matching white blood cell antigens between siblings suggests good HLA compatibility, which lowers GVHD risk; an autograft (using the patient's own tissue) eliminates immune mismatch, so no GVHD risk; unrelated donor or significant HLA differences increase the risk because the immune system sees the graft as foreign.
4. Step 4: Conclude that the most likely factor to increase GVHD risk is a significant difference in HLAs between donor and recipient, as this mismatch triggers the donor immune cells to attack the host tissues.
5. Step 5: Remember that close HLA matching, especially between siblings, is critical in reducing GVHD, and autografts do not cause GVHD since the tissue is from the same individual.