Medical Laboratory Technician Exam Immunology and Serology 4 — Questions and Answers
Question 1: Which of the following best describes the mechanism of action of monoclonal antibodies used in immunoassays?
- They are polyclonal and react with multiple epitopes
- They are derived from a single B cell clone and bind one epitope (Correct answer)
- They are produced by T lymphocytes
- They require complement for antigen detection
Correct answer: They are derived from a single B cell clone and bind one epitope
Monoclonal antibodies are produced by hybridomas derived from a single B cell clone and bind a single specific epitope with high specificity.
Question 2: In a sandwich ELISA, the capture antibody and detection antibody must:
- Be identical immunoglobulins
- Recognize different epitopes on the same antigen (Correct answer)
- Be from the same animal species
- Bind only free antigen, not antibody-bound antigen
Correct answer: Recognize different epitopes on the same antigen
Sandwich ELISA requires two antibodies recognizing non-overlapping epitopes so antigen is 'sandwiched' between capture and labeled detection antibody.
Question 3: A newborn with recurrent bacterial infections, absent tonsils, very low B cells, and very low immunoglobulins most likely has:
- DiGeorge syndrome
- X-linked agammaglobulinemia (Bruton's) (Correct answer)
- Severe combined immunodeficiency
- Common variable immunodeficiency
Correct answer: X-linked agammaglobulinemia (Bruton's)
X-linked agammaglobulinemia is caused by BTK gene mutation, resulting in failure of B cell maturation and absent immunoglobulins in males.
Question 4: Cold agglutinins associated with Mycoplasma pneumoniae infection react with which RBC antigen?
- D antigen
- I antigen (Correct answer)
- K antigen
- Lewis antigen
Correct answer: I antigen
Cold agglutinins from M. pneumoniae infection are IgM autoantibodies directed against the I antigen on adult red blood cells.
Question 5: In nephelometry, the measured signal is:
- Absorbance of transmitted light
- Light scattered at an angle from the incident beam (Correct answer)
- Fluorescence emission after excitation
- Optical density at 450 nm
Correct answer: Light scattered at an angle from the incident beam
Nephelometry measures light scattered by antigen-antibody complexes at a fixed angle, with scatter intensity proportional to complex concentration.
Question 6: Which serologic marker appears first after hepatitis B infection and is used to diagnose acute HBV?
- Anti-HBs
- Anti-HBc IgG
- HBsAg (Correct answer)
- HBeAg
Correct answer: HBsAg
HBsAg (hepatitis B surface antigen) is the first serologic marker to appear after HBV infection, detectable before symptoms develop.
Question 7: Rheumatoid factor (RF) is an autoantibody directed against which target?
- Native dsDNA
- Fc region of IgG (Correct answer)
- Citrullinated peptides
- Histone proteins
Correct answer: Fc region of IgG
Rheumatoid factor is an autoantibody (usually IgM) directed against the Fc region of IgG molecules.
Medical Laboratory Technician Exam Immunology and Serology 4
Which of the following best describes the mechanism of action of monoclonal antibodies used in immunoassays?