Textbook Question
Use the following choices to answer questions 4 and 5:
a. Anti-Brucella
b. Brucella
c. Substrate for the enzyme
Which item is from the patient in an indirect ELISA test?
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Ch. 18 - Practical Applications of Immunology
Tortora14th EditionMicrobiology: An IntroductionISBN: 9780138200398
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Table of contents
- Ch. 1 - The Microbial World and You18
- Ch. 2 - Chemical Principles20
- Ch. 3 - Observing Microorganisms Through a Microscope18
- Ch. 4 - Functional Anatomy of Prokaryotic and Eukaryotic Cells21
- Ch. 5 - Microbial Metabolism20
- Ch. 6 - Microbial Growth20
- Ch. 7 - The Control of Microbial Growth20
- Ch. 8 - Microbial Genetics19
- Ch. 9 - Biotechnology & DNA Technology20
- Ch. 10 - Classification of Microorganisms15
- Ch. 11 - The Prokaryotes: Domains Bacteria and Archaea14
- Ch. 12 - The Eukaryotes: Fungi, Algae, Protozoa, and Helminths17
- Ch. 13 - Viruses, Viroids, and Prions20
- Ch. 14 - Principles of Disease and Epidemiology21
- Ch. 15 - Microbial Mechanisms of Pathogenicity19
- Ch. 16 - Innate Immunity: Nonspecific Defenses of the Host20
- Ch. 17 - Adaptive Immunity: Specific Defenses of the Host20
- Ch. 18 - Practical Applications of Immunology20
- Ch. 19 - Disorders Associated with the Immune System19
- Ch. 20 - Antimicrobial Drugs19
- Ch. 21 - Microbial Diseases of the Skin and Eyes21
- Ch. 22 - Microbial Diseases of the Nervous System19
- Ch. 23 - Microbial Diseases of the Cardiovascular and Lymphatic Systems20
- Ch. 24 - Microbial Diseases of the Respiratory System20
- Ch. 25 - Microbial Diseases of the Digestive System20
- Ch. 26 - Microbial Diseases of the Urinary and Reproductive Systems19
- Ch. 27 - Environmental Microbiology20
- Ch. 28 - Applied and Industrial Microbiology19
Tortora14th EditionMicrobiology: An IntroductionISBN: 9780138200398Not the one you use?Change textbook
Chapter 18, Problem 5
Explain the effects of excess antigen and antibody on the precipitation reaction. How is the precipitin ring test different from an immunodiffusion test?
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Understand the precipitation reaction: it occurs when soluble antigens and antibodies interact to form an insoluble complex that precipitates out of solution. The amount and ratio of antigen to antibody influence the formation of these complexes.
Explain the effect of excess antigen (antigen excess): when there is more antigen than antibody, small soluble complexes form that do not precipitate well, leading to a decrease or absence of visible precipitation. This is called the prozone effect.
Explain the effect of excess antibody (antibody excess): when there is more antibody than antigen, small soluble complexes also form, preventing lattice formation and precipitation. This is known as the postzone effect.
Describe the precipitin ring test: it is a qualitative test where antigen and antibody solutions are layered in a tube, and a visible ring of precipitate forms at the zone of optimal antigen-antibody equivalence, indicating precipitation.
Contrast with the immunodiffusion test: in immunodiffusion, antigen and antibody diffuse through a gel medium (such as agar), and precipitation lines form where optimal concentrations meet. This allows for more detailed analysis of antigen-antibody interactions and can detect multiple antigens or antibodies.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Precipitation Reaction and Antigen-Antibody Interaction
A precipitation reaction occurs when soluble antigens and antibodies form insoluble complexes. The ratio of antigen to antibody is critical; excess antigen or antibody can prevent optimal lattice formation, reducing visible precipitation. This phenomenon is known as the prozone (excess antibody) or postzone (excess antigen) effect.
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Outcomes of Antibody Binding to Antigen
Precipitin Ring Test
The precipitin ring test is a qualitative assay where antigen and antibody solutions are layered in a tube, forming a visible ring of precipitate at the interface if they react. It is simple and rapid, primarily used to detect the presence of specific antibodies or antigens in a sample.
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Immunodiffusion Test
Immunodiffusion involves the diffusion of antigen and antibody in a gel, forming precipitin lines where they meet at optimal concentrations. Unlike the precipitin ring test, it allows for the analysis of multiple antigens or antibodies simultaneously and can provide information about identity, partial identity, or non-identity of antigens.
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Related Practice
Textbook Question
Label components of the direct and indirect ELISA tests in the following situations. Which test is direct? Which test provides definitive proof of disease?
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Textbook Question
How are monoclonal antibodies produced?
Textbook Question
In an immunodiffusion test, a strip of filter paper containing diphtheria antitoxin is placed on a solid culture medium. Then bacteria are streaked perpendicular to the filter paper. If the bacteria are toxigenic,
a. The filter paper will turn red
b. A line of antigen–antibody precipitate will form
c. The cells will lyse
d. The cells will fluoresce
e. None of the above
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Textbook Question
Use the following choices to answer questions 4 and 5:
a. Anti-Brucella
b. Brucella
c. Substrate for the enzyme
Which is the third step in a direct ELISA test?
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Textbook Question
Use the following choices to answer questions 7–9.
a. Direct fluorescent antibody
b. Indirect fluorescent antibody
c. Rabies immune globulin
d. Killed rabies virus
e. None of the above
Treatment given to a person bitten by a rabid bat.
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