Q: Which formula correctly represents the calculation of antibody titer in a serial dilution assay?

$$Titer = \frac{1}{\text{highest dilution showing a positive reaction}}$$

Question 1

Which of the following best describes an attenuated (modified live) vaccine?

Accepted Answer

It uses pathogens with reduced virulence that can still replicate and stimulate immunity.

Question 2

A patient receives a vaccine containing only antigenic fragments of a microbe. Which type of vaccine did they receive?

Accepted Answer

Subunit vaccine

Question 3

Which of the following is a key advantage of ELISA (Enzyme-Linked Immunosorbent Assay) in clinical diagnostics?

Accepted Answer

It can quantify either antigen or antibody and is easy to perform on many samples quickly.

Question 4

Which formula correctly represents the calculation of antibody titer in a serial dilution assay?

Accepted Answer

$$Titer = \frac{1}{	ext{highest dilution showing a positive reaction}}$$

Question 5

A child is given a vaccine that contains a harmless version of a bacterial toxin. What type of vaccine is this?

Accepted Answer

Toxoid vaccine

Question 6

Which of the following is a disadvantage of inactivated (killed) vaccines compared to attenuated vaccines?

Accepted Answer

They often require multiple doses to achieve full immunity.

Question 7

Which laboratory technique is commonly used to determine blood type by observing agglutination?

Accepted Answer

Agglutination test

Question 8

A scientist wants to measure the concentration of antibodies in a patient's serum. Which test should they use?

Accepted Answer

Antibody titer

Question 9

Which of the following best explains why subunit vaccines are considered safer than attenuated vaccines?

Accepted Answer

They contain only specific antigenic fragments, reducing the risk of infection.

Question 10

A patient’s serum is serially diluted and tested for antibody presence. The highest dilution that still shows a positive reaction is 1:128. What is the antibody titer?

Accepted Answer

$$Titer = 128$$

Question 11

Which of the following is a feature of polyclonal vaccines?

Accepted Answer

They contain multiple antigens from different strains or species.

Question 12

In a hemagglutination test, what is being detected?

Accepted Answer

The clumping of red blood cells due to antibodies binding to antigens.

Question 13

Which of the following is a recent development in immune testing that allows for rapid and easy-to-read results?

Accepted Answer

Immunochromatography

Question 14

A patient is tested for HIV using an ELISA. The test detects the presence of which of the following in the patient’s serum?

Accepted Answer

Antibodies specific to HIV antigens

Question 15

Which of the following is a reason why modified live vaccines are not recommended for immunocompromised individuals?

Accepted Answer

They may retain enough residual virulence to cause disease.

Question 16

Which of the following best describes the principle of a direct ELISA?

Accepted Answer

Antigen is bound to the well and detected by a labeled antibody.

Question 17

A laboratory technician is using an indirect ELISA to detect antibodies against a virus. Which step is unique to the indirect ELISA compared to the direct ELISA?

Accepted Answer

Addition of a secondary antibody that binds to the patient’s antibody.

Question 18

Which of the following is a common use of immunochromatography in clinical settings?

Accepted Answer

Pregnancy testing

Question 19

A patient’s serum is tested for antibodies against multiple antigens simultaneously. Which type of test is most appropriate?

Accepted Answer

Antibody microarray

Question 20

Which of the following statements about agglutination tests is correct?

Accepted Answer

They can be used to determine blood type by observing clumping of red blood cells.

Immunization and Applications of the Immune Response 18

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