Immunohistochemistry MCQs

1. 1. What is the purpose of immunohistochemistry (IHC)?
   • A. To stain nuclei
   • B. To identify specific antigens in tissues ✅
   • C. To observe mitosis
   • D. To study DNA replication


2. 2. Which of the following is commonly used as a detection system in IHC?
   • A. Enzymes ✅
   • B. Fluorescent dyes
   • C. Fixatives
   • D. Microtomes


3. 3. What is the role of a primary antibody in IHC?
   • A. To bind directly to enzymes
   • B. To recognize and bind to the target antigen ✅
   • C. To amplify the signal
   • D. To block nonspecific sites


4. 4. What does the term “epitope retrieval” refer to in IHC?
   • A. Fixing tissues
   • B. Embedding tissues in paraffin
   • C. Unmasking antigens for antibody binding ✅
   • D. Staining nuclei


5. 5. Which enzyme is commonly used in IHC for chromogenic detection?
   • A. Horseradish peroxidase (HRP) ✅
   • B. Amylase
   • C. Trypsin
   • D. Lipase


6. 6. What type of control is essential for validating IHC results?
   • A. Negative control ✅
   • B. Positive control
   • C. Replicates
   • D. Non-fixed tissues


7. 7. Which blocking agent is used to reduce nonspecific binding in IHC?
   • A. Bovine serum albumin (BSA) ✅
   • B. Ethanol
   • C. Paraffin
   • D. Acetone


8. 8. What does DAB stand for in IHC staining?
   • A. Diaminobenzidine ✅
   • B. Direct antigen-binding
   • C. DNA-binding antibody
   • D. Detergent-based antigen buffer


9. 9. Which of the following is a common fluorescent dye used in IHC?
   • A. Fluorescein isothiocyanate (FITC) ✅
   • B. Eosin
   • C. Hematoxylin
   • D. Paraffin oil


10. 10. What is the most commonly used fixative for IHC?
    • A. Ethanol
    • B. Formalin ✅
    • C. Acetone
    • D. Xylene


11. 11. Why is heat-induced epitope retrieval (HIER) performed?
    • A. To enhance antibody-antigen interaction ✅
    • B. To reduce nonspecific staining
    • C. To dehydrate tissues
    • D. To fix antigens


12. 12. Which type of antibody is typically used for IHC?
    • A. Polyclonal antibodies
    • B. Monoclonal antibodies ✅
    • C. Secondary antibodies only
    • D. Blocking antibodies


13. 13. What is the purpose of counterstaining in IHC?
    • A. To mask antigen sites
    • B. To provide contrast to the primary stain ✅
    • C. To block nonspecific binding
    • D. To unmask epitopes


14. 14. Which of the following is used to visualize chromogenic IHC results?
    • A. Light microscopy ✅
    • B. Electron microscopy
    • C. Fluorescence microscopy
    • D. Confocal microscopy


15. 15. What is the role of a secondary antibody in IHC?
    • A. To bind directly to the antigen
    • B. To amplify the signal of the primary antibody ✅
    • C. To act as a blocking agent
    • D. To fix tissues


16. 16. Which buffer is commonly used in IHC procedures?
    • A. Phosphate-buffered saline (PBS) ✅
    • B. Acetate buffer
    • C. Citrate buffer
    • D. Sodium hydroxide


17. 17. What is the main advantage of using IHC over traditional staining methods?
    • A. Identifies specific proteins in tissues ✅
    • B. Provides a clearer view of nuclei
    • C. Requires no antibodies
    • D. Uses simpler protocols


18. 18. Which of the following can cause false negatives in IHC?
    • A. Overfixation ✅
    • B. Overstaining
    • C. Low antibody concentration
    • D. Blocking nonspecific binding


19. 19. What is the optimal pH for antigen retrieval in IHC?
    • A. 4.5-5.5
    • B. 6.0-7.0 ✅
    • C. 8.0-9.0
    • D. 9.5-10.5


20. 20. Which chromogen produces a brown-colored reaction product in IHC?
    • A. DAB ✅
    • B. FITC
    • C. HRP
    • D. Alexa Fluor