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': 'Prozone phenomenon is due to: \nSelect and explain. \nA. Antigen excess, B. Antibody excess, C. Excessive immune complex, D. Acute phase reactants', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ans: B (Antibody excess) Ref: Ananthonaravan. Panikar CJ Textbook of .Microbiology. 8th Edition. John Wiley & Sons: 2009. Pg. 104Explanation:Antigen and antibody can combine in various proportions.State of antibody excess - ProzoneOptimal ratio - Zone of equivalenceState of antigen excess - Postzone (See the following figure)The prozone is very important in serodiagnosisSera rich in antibody may sometimes give a false negative precipitation or agglutination resultE.g. Patients with Brucellosis are known to exhibit prozone phenomenonThe serum should be diluted several times when prozone phenomenon is suspected', 'role': 'assistant'}]