Medical Technologist Test Immunology and Serology 2 — Questions and Answers
Question 1: Which hepatitis B serological marker is the FIRST to appear in serum during acute infection?
- Anti-HBs
- HBsAg (Correct answer)
- Anti-HBc IgG
- HBeAg
Correct answer: HBsAg
HBsAg (hepatitis B surface antigen) is the earliest detectable marker in serum, appearing during the incubation period before clinical symptoms.
Question 2: The RPR (Rapid Plasma Reagin) test for syphilis uses which antigen?
- Treponema pallidum lysate
- Cardiolipin-lecithin-cholesterol (Correct answer)
- Purified treponemal protein
- Fluorescent-labeled Treponema
Correct answer: Cardiolipin-lecithin-cholesterol
The RPR is a nontreponemal test using a cardiolipin-lecithin-cholesterol antigen to detect reagin antibodies produced during syphilis infection.
Question 3: The prozone phenomenon in serology results in a false-negative reaction due to:
- Antigen excess preventing lattice formation
- Antibody excess preventing lattice formation (Correct answer)
- Incorrect reaction temperature
- Improper pH of the buffer
Correct answer: Antibody excess preventing lattice formation
Prozone occurs when antibody greatly exceeds antigen, saturating all antigen binding sites and preventing the cross-linking necessary for a visible reaction.
Question 4: Which test is used as a CONFIRMATORY assay for HIV infection following a reactive screening result?
- ELISA
- Western blot (Correct answer)
- Rapid plasma reagin
- Particle agglutination
Correct answer: Western blot
Western blot identifies antibodies against specific HIV proteins (e.g., gp120, gp41, p24) separated by molecular weight and serves as the confirmatory test.
Question 5: C-reactive protein (CRP) is produced primarily by which organ during the acute phase response?
- Spleen
- Bone marrow
- Liver (Correct answer)
- Lymph nodes
Correct answer: Liver
CRP is an acute phase protein synthesized by hepatocytes in the liver in response to IL-6 released during inflammation or infection.
Question 6: The Weil-Felix test uses Proteus OX antigen strains to diagnose infections caused by:
- Rickettsia species (Correct answer)
- Brucella species
- Leptospira species
- Borrelia burgdorferi
Correct answer: Rickettsia species
Weil-Felix exploits cross-reactive antigens shared between certain Rickettsia species and Proteus OX2, OX19, and OXK strains to detect rickettsial infections.
Question 7: Which complement component is shared by ALL three activation pathways (classical, alternative, and lectin)?
- C1q
- C3 (Correct answer)
- Factor B
- MASP-1
Correct answer: C3
C3 is the central convergence point of all three complement pathways; its cleavage to C3a and C3b is the pivotal step in complement activation.
Medical Technologist Test Immunology and Serology 2
Which hepatitis B serological marker is the FIRST to appear in serum during acute infection?