This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pathology
[{'content': 'Most important antigen initiating graft rejection \nSelect and explain. \nA. MHC - molecule, B. Polysaccharide, C. DHA, D. HLA - Antigen', 'role': 'user'}, {'content': 'Answer: D \nExplanation: the most important consequence of direct recognition is the activation of CD8+ T cells \nwhich recognise class I MHC molecules in the graft.Host CD4+ helper T cell may be triggered into proliferation and cytokine production by recognition of donor\nclass II MHC molecules \xa0and drive an inflammatory response', 'role': 'assistant'}]