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': 'Binding of complement to bacterial cell surface is called: \nSelect and explain. \nA. Opsonisation, B. Complement activation, C. Complement stabilization, D. None of the above', 'role': 'user'}, {'content': 'Answer: A \nExplanation: The microorganisms are coated with specific proteins, opsonins\xa0from the serum and the process is called opsonisation (meaning preparing for eating).\xa0\nOpsonins establish a bond between bacteria and the cell membrane of phagocytic cell.\xa0\nThe main opsonins present in the serum and their corresponding receptors on the surface of phagocytic cells (PMNs or macrophages) are as under:\n\ni) IgG opsonin is the Fc fragment of immunoglobulin G; it is the naturally-occurring antibody in the serum that coats the bacteria, while the PMNs possess receptors for the same.\nii) C3b opsonin is the fragment generated by activation of complement pathway. It is strongly chemotactic for attracting PMNs to bacteria.\niii) Lectins are carbohydrate-binding proteins in the plasma which bind to bacterial cell wall.', 'role': 'assistant'}]