ASCP Immunology and Serology 2 — Questions and Answers
Question 1: Which complement pathway is initiated by antibody-antigen complexes?
- Alternative pathway
- Lectin (MBL) pathway
- Classical pathway (Correct answer)
- Terminal pathway only
Correct answer: Classical pathway
The classical complement pathway is activated by IgG or IgM antibodies bound to antigen, triggering C1q binding.
Question 2: The Western blot test for HIV confirmation detects antibodies against which viral proteins?
- Viral RNA polymerase subunits
- p24 core, gp41 envelope, and gp120/160 envelope proteins (Correct answer)
- HLA antigens on lymphocytes
- CD4 receptor complexes
Correct answer: p24 core, gp41 envelope, and gp120/160 envelope proteins
HIV Western blot detects antibodies to viral core (p24, p17) and envelope (gp41, gp120, gp160) proteins separated by electrophoresis.
Question 3: Anti-CCP (anti-cyclic citrullinated peptide) antibodies are most specific for:
- Systemic lupus erythematosus
- Rheumatoid arthritis (Correct answer)
- Sjögren's syndrome
- Polymyositis
Correct answer: Rheumatoid arthritis
Anti-CCP antibodies have >90% specificity for rheumatoid arthritis and can appear years before clinical symptoms.
Question 4: The indirect fluorescent antibody (IFA) test for ANA uses which substrate?
- Sheep red blood cells
- HEp-2 (human epithelial) cells (Correct answer)
- Rabbit liver sections
- Cardiolipin-coated microplates
Correct answer: HEp-2 (human epithelial) cells
HEp-2 cells are the standard substrate for ANA IFA because their large nuclei display multiple patterns (homogeneous, speckled, nucleolar, centromere).
Question 5: Which marker is used to diagnose infectious mononucleosis caused by Epstein-Barr virus?
- Monospot test (heterophile antibodies) plus EBV-specific antibodies (Correct answer)
- VDRL test
- Anti-HBc IgM
- Cold agglutinins
Correct answer: Monospot test (heterophile antibodies) plus EBV-specific antibodies
The monospot detects heterophile antibodies that agglutinate horse/sheep RBCs; EBV-specific tests (VCA-IgM, EA, EBNA) confirm diagnosis.
Question 6: Flow cytometry is used to enumerate CD4+ T cells in HIV patients to:
- Detect viral RNA load
- Monitor immune status and guide antiretroviral therapy initiation (Correct answer)
- Diagnose opportunistic infections
- Measure antibody titers
Correct answer: Monitor immune status and guide antiretroviral therapy initiation
CD4+ cell counts below 200 cells/µL define AIDS and indicate the threshold for opportunistic infection prophylaxis and ART monitoring.
ASCP Immunology and Serology 2
Which complement pathway is initiated by antibody-antigen complexes?