Deck 10: Serologic Diagnosis of Infectious Diseases

Question 1

Antibody-mediated immune responses produced by specific proteins are generated by:

A) lymphocytes of the T class.
B) lymphocytes of the B class.
C) neutrophils.
D) basophils.

Answer 1

B
B lymphocytes produce immunoglobulins, which they secrete into blood or lymphatic and other body fluids.

Question 2

Neutralizing antibodies are those that function by:

A) attaching to the surface of pathogens and contributing to their destruction by the lytic action of complement.
B) binding to and blocking surface receptors for host cells.
C) attaching to the surface of pathogens and making the pathogens more amenable to ingestion by phagocytic cells.
D) attaching to the surface of pathogens and contributing to their destruction by chemotaxis.

Answer 2

B
Antibodies function in different ways.Neutralizing antibodies work by binding to and blocking surface receptors for host cells.

Question 3

A patient was suspected of having a rickettsial infection after hiking in the Rocky Mountains.A Weil-Felix test was performed, which resulted in no agglutination observed.Which one of the following statements explains this discrepancy?

A) Detection of rickettsial infections using strains of Proteus is not as specific as other serologic tests; therefore the infections should be retested with a newer method.
B) The Weil-Felix test is not the appropriate test to order; it cannot detect cross-reacting antibodies.
C) Rickettsial antibodies should be tested using the fluorescent treponemal antibody absorption (FTA-ABS) test, not the Weil-Felix test.
D) No discrepancy is present. Rickettsial antibodies do not agglutinate with Proteus antigens.

Answer 3

A
The Weil-Felix test is an older method and is not as sensitive as some of the newer tests; therefore infections should be retested to ensure an accurate result.

Question 4

Elevations of which of the following antibodies may indicate a parasitic infection?

A) IgG
B) IgA
C) IgM
D) IgE

Question 5

A positive test was observed on a serum sample that resulted in the formation of a fine precipitate on a reaction card.The most likely organism serologically identified is:

A) Chlamydia trachomatis.
B) Bacillus anthracis.
C) Treponema pallidum.
D) Toxoplasma gondii.

Question 6

A Western blot assay was performed, and bands were observed at p24, p41, and gp120/160 (kilodaltons).The organism can be identified as:

A) herpes simplex virus.
B) human immunodeficiency virus (HIV).
C) Borrelia burgdorferi.
D) Treponema pallidum.

Question 7

The immunochemical test that involves the agglutination of an artificial carrier particle with the antigen bound to its surface and an antibody present in a specimen is referred to as:

A) double immunodiffusion.
B) counterimmunoelectrophoresis.
C) particle agglutination.
D) enzyme immunoassay.

Question 8

The precipitin test that is widely used for detecting antibodies against fungal infection is referred to as:

A) double immunodiffusion.
B) counterimmunoelectrophoresis.
C) particle agglutination.
D) enzyme immunoassay.

Question 9

Specific proteins produced by cells of the immune system in response to the presence of foreign molecules that circulate in the serum and are present in secretions such as saliva are called:

A) antigens.
B) immunoglobulins.
C) cytokines.
D) phagogens.

Question 10

The difference between latex agglutination and hemagglutination is:

A) the type of particle used to carry the antibody.
B) the type of target organism involved.
C) that hemagglutination is less specific but more sensitive.
D) that hemagglutination procedures are temperature sensitive.

Question 11

The antibody that is predominantly found in tears, saliva, and intestinal secretions is:

A) IgG.
B) IgA.
C) IgM.
D) IgE.

Question 12

Cell-mediated immune responses, such as attacking and killing microorganisms or host cells that are damaged or infected, are carried out by:

A) lymphocytes of the thymus-derived (T) class.
B) lymphocytes of the bone marrow-derived (B) class.
C) neutrophils.
D) nasophils.

Question 13

A pregnant woman had contact with her nephew who was just diagnosed with a rubella infection.Acute and convalescent samples were taken, which resulted in an acute titer of 1:16 and a convalescent titer of 1:32.Which one of the following comments explains the risk to the fetus?

A) The risk is low; a fourfold rise in titer is not present.
B) The risk is high; more than a fourfold rise is present in titer.
C) The risk is high because both titers are elevated.
D) Rubella is not a congenital disease; therefore the test should not have been ordered.

Question 14

The presence of which of the following antibodies usually indicates a recent or an active infection?

A) Immunoglobulin (Ig) G
B) IgA
C) IgM
D) IgE

Question 15

A method that uses an electrical current to speed up the migration of an antigen and antibody is referred to as:

A) double immunodiffusion.
B) counterimmunoelectrophoresis.
C) particle agglutination.
D) enzyme immunoassay.

Question 16

For most pathogens to be diagnostic of current infection, there must be a(n)_____ in the patient's antibody titer of _____ doubling dilutions.

A) decrease; two
B) increase; two
C) decrease; four
D) increase; four

Question 17

The study of the diagnosis of disease by measuring antibody levels in serum is called:

A) immunology.
B) immunohematology.
C) serology.
D) immunocytology.

Question 18

Complement-fixing antibodies are those that function by:

A) attaching to the surface of pathogens and contributing to their destruction by the lytic action of complement.
B) binding to and blocking surface receptors for host cells.
C) attaching to the surface of pathogens and making the pathogens more amenable to ingestion by phagocytic cells.
D) attaching to the surface of pathogens and contributing to their destruction by chemotaxis.

Question 19

Opsonizing antibodies are those that function by:

A) attaching to the surface of pathogens and contributing to their destruction by the lytic action of complement.
B) binding to and blocking surface receptors for host cells.
C) attaching to the surface of pathogens and making the pathogens more amenable to ingestion by phagocytic cells.
D) attaching to the surface of pathogens and contributing to their destruction by chemotaxis.

Question 20

For an accurate diagnostic of a current infection, acute and convalescent sera should reflect a(n)_____ in the patient's antibody titer of _____ doubling dilutions.

A) decrease; two
B) increase; two
C) decrease; four
D) increase; four