CMLA Immunology & Serology 2

Question 1

What principle does the ELISA (Enzyme-Linked Immunosorbent Assay) use to detect antibodies or antigens?

Accepted Answer

Enzyme-labeled antibodies producing a colorimetric signal

Answer

Precipitation of immune complexes in agar

Answer

Fluorescent dyes visualized under UV light

Answer

Agglutination of sensitized red blood cells

Question 2

In serological testing, agglutination indicates:

Accepted Answer

Cross-linking of particulate antigens by antibodies causing visible clumping

Answer

Lysis of cells by complement activation

Answer

Precipitation of soluble antigen-antibody complexes

Answer

Viral neutralization by specific antibodies

Question 3

What is the purpose of including a positive control in a serological assay?

Accepted Answer

To verify the test system produces a positive result with known positive material

Answer

To ensure reagents are free from contamination

Answer

To calibrate spectrophotometer readings

Answer

To identify non-specific background binding

Question 4

In indirect fluorescent antibody (IFA) testing, the fluorescent-labeled secondary antibody binds to:

Accepted Answer

The patient's primary antibody already bound to antigen

Answer

The target antigen on the substrate directly

Answer

The substrate membrane

Answer

The cell surface receptors

Question 5

What does a serum antibody titer measure?

Accepted Answer

The highest dilution of serum still showing a positive reaction

Answer

The total protein concentration in serum

Answer

The rate of antibody synthesis per hour

Answer

The molecular weight of the detected antibody

Question 6

Which non-treponemal test is used as a screening test for syphilis?

Accepted Answer

RPR (Rapid Plasma Reagin)

Answer

Weil-Felix test

Answer

Westergren ESR test

Answer

Direct Coombs test

Question 7

In a precipitation reaction, the zone of equivalence refers to:

Accepted Answer

The point where antigen and antibody concentrations allow maximum lattice formation and precipitation

Answer

The pH optimum for antigen-antibody binding

Answer

The temperature at which precipitation occurs

Answer

The complement concentration needed for lysis