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Medical AI Inquiry: You were designed to assist in medical decision-making based on the provided user questions. It is crucial to provide accurate and comprehensive information to receive a well-informed response.
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An immunologist is conducting an experiment to understand precipitation reactions. He notes that on adding excessive amount of antibody to a serum sample containing small amount of antigen, the amount of precipitate formed is less, compared to adding smaller amount of antibody to the same sample. What is this phenomenon called?
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The correct answer is  Lattice hypothesis explains this: In precipitation reactions, the amount of precipitate formed is greatly influenced by the relative propoions of antigens and antibodies. Pro-zone phenomenon: It is caused by excessive antibody in the test system. (Weak or even absent precipitation and a false negative test) Zone of equivalence: Antigen and antibody are in optimum propoions and maximum precipitation occurs. Post-zone phenomenon: Presence of excessive antigen in the test system. (Weaker or even absent precipitation) Reference: Ananthanarayan and Paniker&;s Textbook of Microbiology Tenth edition