This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Organ Transplant / Graft, Subject name: Pathology
Organs affected in Graft vs Host reaction are: 
Select and explain. 
A. Skin, B. GIT, C. Liver, D. All of the above
D: All of the above
Answer: D: All of the above 
Explanation: GVHD occurs when immunologically competent cells or their precursors are transplanted into immunologically incompetent recipients, and the transferred cells recognize allo-antigens in the host tissues and attack them leading to destruction.. Acute GVHD occurs within days to weeks after allogeneic bone marrow transplantation. Although any organ may be affected, the major clinical manifestations result from involvement of:- The immune system Epithelia of the skin It is believed that in addition to direct cytotoxicity by CD8+ T cells, considerable damage is inflicted by cytokines released by the sensitized donor T cells.