This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Immunology, Subject name: Microbiology
[{'content': "An idiotype is characterized by \nSelect and explain. \nA. Determinant exposed after papain cleavage to an F(ab')2 fragment, B. Determinant from one clone of cells and probably located close to the antigenbinding site of the immunoglobulin, C. Determinant inherited in a Mendelian fashion and recognized by crossimmunization of individuals in a species, D. Heavy-chain determinant recognized by heterologous antisera", 'role': 'user'}, {'content': 'Answer: B \nExplanation: Idiotypes are antigenic determinants that appear only on the Fab fragments of antibodies and appear to be localized at the ligand-binding site; thus, anti-idiotype antisera may block reactions with the appropriate hapten. The carbohydrate side chains of immunoglobulins are relatively nonimmunogenic. New determinants may be exposed after papain cleavage of immunoglobulins, but these determinants are not included in the classification of the native molecule. Reference: Ananthanarayan and Paniker&;s Textbook of Microbiology Tenth edition', 'role': 'assistant'}]