Medical Technologist Test Immunology and Serology 1 — Questions and Answers
Question 1: Which immunoglobulin class is the FIRST to be produced during a primary immune response?
- IgG
- IgM (Correct answer)
- IgA
- IgE
Correct answer: IgM
IgM is the first antibody produced during a primary immune response before class switching to IgG and other isotypes occurs.
Question 2: The complement pathway activated directly by antigen-antibody complexes is the:
- Lectin pathway
- Alternative pathway
- Classical pathway (Correct answer)
- Mannose-binding pathway
Correct answer: Classical pathway
The classical complement pathway is triggered when C1q binds to antigen-antibody (immune) complexes, initiating the cascade.
Question 3: Type I hypersensitivity (anaphylactic) reactions are primarily mediated by which immunoglobulin?
- IgG
- IgM
- IgA
- IgE (Correct answer)
Correct answer: IgE
Type I hypersensitivity is mediated by IgE antibodies bound to mast cells and basophils, causing degranulation upon antigen re-exposure.
Question 4: A homogeneous ANA fluorescence pattern is most commonly associated with antibodies against:
- Anti-Sm antibodies
- Anti-dsDNA or anti-histone antibodies (Correct answer)
- Anti-SSA/Ro antibodies
- Anti-centromere antibodies
Correct answer: Anti-dsDNA or anti-histone antibodies
A homogeneous ANA pattern reflects antibodies against double-stranded DNA or histone proteins and is classically associated with systemic lupus erythematosus.
Question 5: In the zone of equivalence during a precipitation reaction, which of the following occurs?
- Antigen is in excess, inhibiting precipitate
- Antibody is in excess, inhibiting precipitate
- Optimal lattice formation produces maximum precipitate (Correct answer)
- No precipitation occurs due to soluble complexes
Correct answer: Optimal lattice formation produces maximum precipitate
In the zone of equivalence, antigen and antibody are present in optimal proportions, allowing maximum cross-linked lattice formation and precipitation.
Question 6: Rheumatoid factor (RF) is an autoantibody directed against which target?
- Double-stranded DNA
- The Fc portion of IgG (Correct answer)
- Histone proteins
- Cyclic citrullinated peptides (CCP)
Correct answer: The Fc portion of IgG
Rheumatoid factor is typically an IgM autoantibody that binds to the Fc region of IgG molecules, forming immune complexes in rheumatoid arthritis.
Question 7: Which technique uses fluorescent-labeled antibodies to detect antigens in tissue sections or cells?
- Ouchterlony double diffusion
- Direct immunofluorescence (Correct answer)
- Latex agglutination
- Rocket electrophoresis
Correct answer: Direct immunofluorescence
Direct immunofluorescence uses fluorochrome-conjugated antibodies applied directly to tissue or cells to visualize specific antigens under a fluorescence microscope.
Medical Technologist Test Immunology and Serology 1
Which immunoglobulin class is the FIRST to be produced during a primary immune response?