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': 'Impoant step in activation of naive CD 4+ T cells and initiation of cell mediated immune response is played by Interleukin? \nSelect and explain. \nA. 1, B. 2, C. 3, D. 4', 'role': 'user'}, {'content': "Answer: B \nExplanation: Ans. is 'b' i.e., 2 Activation of CD4+ T Cells: Naive CD4+ T cells recognize peptides displayed by dendritic cells and secrete IL-2, which functions as an autocrine growth factor to stimulate proliferation of the antigen- responsive T cells. The subsequent differentiation of antigen-stimulated T cells to TH1 or TH17 cells is driven by the cytokines produced by APCs at the time of T-cell acti- vation. In some situations the APCs (dendritic cells and macrophages) produce IL-12, which induces differentiation of CD4+ T cells to the TH1 subset. IFN-y produced by these effector cells promotes fuher TH1 development, thus amplifying the reaction. If the APCs produce inflammatory cytokines such as IL-1, IL-6, and a close relative of IL-12 called IL-23, these stimulate differentiation of T cells to the TH17 subset.", 'role': 'assistant'}]