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: Microbiology
[{'content': 'Membrane attack complex is - \nSelect and explain. \nA. C5-9, B. C3b, C. C1-3, D. C4-5', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Components of complement cascade mediate various biological responses\n\n\xa0C5a, C3a, to a lesser extent C4a → are called anaphylotoxin because they have effects similar to those of\xa0mast cell mediators that are involved in the reaction\xa0called anaphylaxis. These effects are due to\xa0stimulation\xa0of histamine release by this anaphylatoxin. The effects are increased vascular permeability\xa0and vasodilatation.\n\xa0C5a\xa0is a powerful chemotactic\xa0agent\n\xa0C3b, C3bi act as an opsonin and enhance phagocytosis.\n\xa0C called membrane attack\xa0complex (MAC). It forms a channel in the lipid membrane and causes cell lysis\xa0(including bacteria).', 'role': 'assistant'}]