Question 1

An ELISA for Hepatitis C has 95 percent sensitivity and 90 percent specificity.This means that the test

Accepted Answer

Sensitivity refers to the test's ability to correctly identify those with the disease (true positive rate), which is 95% in this case. Specificity refers to the test's ability to correctly identify those without the disease (true negative rate), which is 90% here, meaning the false positive rate is 10%.

Question 2

Which of the following are sources of antibodies for serological testing?

Accepted Answer

Antibodies for serological testing can be sourced from vaccinated animals, where the immune response generates specific antibodies, and from cells that are engineered to produce monoclonal antibodies, which are identical and target a specific antigen. Viral cultures are not a source of antibodies but rather a method to grow viruses for study or vaccine production.

Question 3

A test used to detect anti-Rickettsia antibodies in a patient's serum is the

Accepted Answer

The indirect fluorescent-antibody test is used to detect antibodies (IgG, IgM, IgA) against Rickettsia antigens in a patient's serum. It involves adding a known Rickettsia antigen to the patient's serum, then adding a fluorescent-labeled secondary antibody that binds to any antibodies in the patient's serum that recognize the Rickettsia antigen. The test is considered indirect because it detects the presence of antibodies instead of directly detecting the antigen itself. This test is commonly used to diagnose infections such as Rocky Mountain spotted fever and typhus.

Question 4

Patient's serum,influenza virus,and red blood cells are mixed in a tube.What happens if the patient has antibodies against influenza virus?

Accepted Answer

If the patient has antibodies against influenza virus, they will bind to the virus and prevent hemagglutination, leading to hemagglutination-inhibition. Agglutination occurs when the antibodies bind to red blood cells, which is not the case here. Complement fixation and hemolysis involve other mechanisms and are not relevant in this scenario.

Question 5

The clumping of test red blood cells indicates a negative test result (no antibodies against the virus in the patient's serum)in the

Accepted Answer

The answer of The clumping of test red blood cells...

Question 6

A reaction that uses the absence of hemolysis of red blood cells to indicate an antigen-antibody reaction is called a(n)

Accepted Answer

The absence of hemolysis of red blood cells indicates that complement has not been activated, meaning that the antigen-antibody reaction has occurred and the complement system is not needed to lyse the cells. This is a characteristic of complement fixation reactions. Agglutination, immunofluorescence, neutralization, and precipitation reactions do not involve the complement system in the same way.

Question 7

Purified protein from Bordetella pertussis is used in a(n)

Accepted Answer

Purified protein from Bordetella pertussis is used in a subunit vaccine, where only the antigenic portion of the pathogen is used to elicit an immune response. Conjugated vaccines use a polysaccharide antigen conjugated to a carrier protein, nucleic acid vaccines use genetic material encoding the antigen, attenuated whole-agent vaccines use a weakened form of the pathogen, and toxoid vaccines use inactivated toxins.

Question 8

What type of vaccine is the live,weakened measles virus?

Accepted Answer

The live, weakened measles virus vaccine is an attenuated whole-agent vaccine. This vaccine contains a version of the live virus that has been weakened so that it can stimulate an immune response without causing illness. This type of vaccine is highly effective in producing immunity to the measles virus.

Question 9

Which of the following is a pregnancy test used to find the fetal hormone HCG in a woman's urine using anti-HCG and latex spheres?

Accepted Answer

The correct answer is indirect agglutination reaction. In this method, anti-HCG antibodies are attached to latex spheres. When a woman's urine containing HCG is added, it binds to the anti-HCG on the spheres, causing them to clump together (agglutinate), indicating a positive pregnancy test. This is an example of an indirect agglutination reaction because it involves the use of particles (latex spheres) coated with antibodies to detect the presence of antigens (HCG).

Question 10

A DNA plasmid encoding a protein antigen from West Nile virus is injected into muscle cells of a horse.This is an example of a(n)

Accepted Answer

Injecting a DNA plasmid encoding a protein antigen is an example of a nucleic acid vaccine. This type of vaccine introduces genetic material (DNA or RNA) into the body, leading to the production of the antigen by the host cells. The immune system then recognizes and responds to the antigen, providing immunity against the virus.

Question 11

Toxoid vaccines,such as the vaccines against diphtheria and tetanus,elicit a(n)

Accepted Answer

Toxoid vaccines are made from inactivated bacterial toxins that have been treated with chemicals or heat to eliminate their harmful effects while preserving their antigenicity. When the toxoid vaccine is administered, it triggers an immune response that leads to the production of specific antibodies against the bacterial toxin. This antibody response provides protection against the disease caused by the bacteria that produce the toxin. Therefore, the best choice is D, which states that toxoid vaccines elicit an antibody response against these bacterial toxins.

Question 12

Which of the following is a test to determine a patient's blood type by mixing the patient's red blood cells with antisera?

Accepted Answer

The direct agglutination reaction is a test that determines a patient's blood type by mixing the patient's red blood cells with antisera. The antigen-antibody reaction results in either agglutination (clumping) or no agglutination depending on the blood type. This is used to determine the presence of ABO and Rh antigens.

Question 13

A test used to identify antibodies against Treponema pallidum in a patient's serum is the

Accepted Answer

The indirect fluorescent-antibody test is commonly used to detect antibodies against Treponema pallidum, the bacteria that causes syphilis. In this test, patient serum is first exposed to a known antigen, followed by a fluorescently-tagged secondary antibody that will bind to any IgG antibodies present in the serum. If there are antibodies in the serum that recognize the Treponema pallidum antigen, they will bind to the antigen, which will then be detected by the secondary antibody. This secondary antibody will also bind to any antibodies present, allowing for visualization of the positive reaction by fluorescence microscopy.

Question 14

A patient shows the presence of antibodies against diphtheria toxin.Which of the following statements is FALSE?

Accepted Answer

Antibodies against diphtheria toxin can be produced in response to vaccination or previous infection with the bacterium that causes diphtheria. However, the presence of antibodies alone does not necessarily indicate current or past infection. It is possible that the patient was in close contact with someone who had the disease, leading to the production of antibodies.

Question 15

What type of vaccine involves host synthesis of viral antigens?

Accepted Answer

Nucleic acid vaccines, such as DNA and RNA vaccines, involve the host's cells taking up the nucleic acid and then using the host's cellular machinery to synthesize the viral antigen. This process mimics the natural infection process, leading to an immune response.

Question 16

A test used to identify Streptococcus pyogenes in a patient's throat swab is the

Accepted Answer

The direct fluorescent-antibody test is the most commonly used test to identify Streptococcus pyogenes in a patient's throat swab. It involves using antibodies labeled with fluorescent dye to detect the presence of the bacteria.

Question 17

In an agglutination test,eight serial dilutions to determine antibody titer were set up.Tube #1 contained a 1:2 dilution;tube #2,a 1:4,etc.If tube #6 is the last tube showing agglutination,what is the antibody titer?

Accepted Answer

The answer of In an agglutination test,eight serial dilutions to...

Question 18

A reaction between antibody and particulate antigen is called a(n)

Accepted Answer

Agglutination reaction is the clumping together of cells or particles, caused by the cross-linking of antigen-antibody complexes.

Question 19

All of the following are generally used in vaccines EXCEPT

Accepted Answer

Antibodies are not generally used in vaccines. Vaccines typically contain either weakened or dead pathogens or pieces of pathogens, such as bacterial cells or viral particles, or in the case of toxoid vaccines, inactivated toxins. The purpose of vaccination is to stimulate the immune system to produce its own antibodies against the pathogen, not to provide pre-formed antibodies.

Question 20

A reaction between an antibody and soluble antigen,forming larger,interlocking molecular lattices,is called a(n)

Accepted Answer

The formation of larger, interlocking molecular lattices between an antibody and soluble antigen is characteristic of a precipitation reaction. This reaction occurs when the antigen and antibody combine in the presence of electrolytes to form an insoluble lattice-like structure that settles out of solution. Agglutination involves visible clumping of cells or particles, while complement fixation and neutralization reactions involve other mechanisms of antigen-antibody interaction. Immunofluorescence involves the labeling of specific molecules with fluorescent tags for visualization.

Quiz 18: Practical Applications of Immunology