This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Bacteria, Subject name: Microbiology
[{'content': 'True about protein A of staph aureus: \nSelect and explain. \nA. Causes opsonization, B. Binds to Fc portion of IgG, C. Stimulate phagocytosis, D. T-cell mitogen', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ans. is \'b\' i.e., Binds to Fc part of IgG(Ref: Ananthanarayan, 9th/e, p. 197, 198)* Protein A is a cell wall component of S aureus strains and is a bacterial surface protein called as microbial surface components recognizing adhesive matrix molecules (MSCRAMMs).Bacterial attachment to host cells is mediated by MSCRAMMs, and these are important virulence factors.Protein A of Staph aureus binds to Fc terminal of IgG (IgG 1, 2 and 4 but not IgG 3) and prevents opsono- phagocytosis by PMNs.* Protein A has become an important reagent in immunology and diagnostic laboratory technology; for example, protein A with attached IgG molecules directed against a specific bacterial antigen agglutinates bacteria that have that antigen ("conglutination").', 'role': 'assistant'}]