What are the three reagents required in the Basic Peroxidase-Antiperoxidase (PAP) immunoperoxidase procedure?

• A. Primary Ab, Secondary Ab, PAP complex
• B. PBS solution, AEC, Primary Ab
• C. Primary Ab, Biotinylated Ab, Avidin
• D. Tissue, blocking serum, chromogen

Answer: (A)

In the Basic PAP immunoperoxidase procedure, the essential reagent trio forms a sandwiched enzyme signal at the antigen site. The primary antibody binds the target antigen in the tissue. A secondary antibody recognizes and binds to that primary antibody, tagging the complex. The PAP complex (peroxidase-antiperoxidase) then binds to the secondary antibody, delivering the peroxidase enzyme to the site. When a chromogenic substrate is added afterward, the peroxidase catalyzes a color reaction that visualizes the labeled cells.

Other elements like washing buffers, blocking serum, or the chromogen themselves are part of the workflow or visualization, but the three core reagents that establish the enzyme-labeled sandwich are the primary antibody, the secondary antibody, and the PAP complex.