HTL Immunohistochemistry & Special Stains 2

Question 1

Which antigen retrieval method uses a microwave or pressure cooker with citrate buffer to unmask epitopes?

Accepted Answer

Heat-induced epitope retrieval (HIER)

Answer

HIER uses heat applied in citrate buffer (pH 6) or EDTA buffer (pH 9) to reverse formalin cross-links and unmask epitopes.

Question 2

In the ABC (avidin-biotin complex) IHC detection method, which molecule bridges the primary antibody signal to the enzyme?

Accepted Answer

Biotinylated secondary antibody plus preformed avidin-biotin-enzyme complex

Answer

The ABC method uses a biotinylated secondary antibody that binds the preformed avidin-biotin-enzyme complex, amplifying signal.

Question 3

A Masson's trichrome stain produces which color combination for collagen versus muscle?

Accepted Answer

Collagen blue/green, muscle red

Answer

Masson's trichrome stains collagen blue or green and muscle (cytoplasm) red, with nuclei staining dark.

Question 4

Which special stain is used specifically to demonstrate fungi, including Pneumocystis jirovecii, in tissue sections?

Accepted Answer

Grocott methenamine silver (GMS)

Answer

GMS (Gomori methenamine silver) stains fungal cell walls black by reducing silver ions, and is the preferred stain for Pneumocystis.

Question 5

Endogenous biotin activity is a common source of background in IHC. Which tissue type is most problematic?

Accepted Answer

Kidney and liver

Answer

Liver and kidney contain high levels of endogenous biotin, causing non-specific background in biotin-based detection systems.

(HTL) Histotechnology Certification Practice Test