Question

Which technique is best suited for identifying a specific protein in a formalin-fixed paraffin-embedded (FFPE) tissue section?

• A. Immunohistochemistry (IHC)
• B. Fluorescence in situ hybridization (FISH)
• C. Western blot
• D. Flow cytometry

Hint:

You need antibody-based protein detection that keeps tissue architecture intact.

Answer 1

The Correct Option is A

Step 1: Understand the substrate.
An FFPE section is a fixed, paraffin-embedded tissue slice mounted on a slide, preserving tissue architecture. The question asks specifically about detecting a protein while keeping it in situ.

Step 2: Match the technique.
Immunohistochemistry (IHC) uses antibodies directed against the target protein, with a chromogenic (e.g. DAB) or enzymatic readout, applied directly to the tissue section. It localises the protein within specific cells/compartments while preserving morphology - ideally suited to FFPE sections.

Step 3: Why the other options are wrong.
• FISH - detects nucleic acids (DNA/RNA sequences), not proteins.
• Western blot - detects proteins but requires tissue lysis/homogenisation and gel electrophoresis; it loses spatial/architectural information and is not performed on intact sections.
• Flow cytometry - requires a single-cell suspension, not a solid fixed section.

Key fact: IHC is the method of choice for in-situ protein identification on FFPE tissue.