In ABC-immunoperoxidase, what does ABC stand for?

• A. Avidin-Biotin Complex
• B. Antibody-Biotin Complex
• C. Alkaline Biotin Complex
• D. Autoclave Biotin Complex

Answer: (A)

Signal amplification in immunoperoxidase relies on the strong interaction between avidin and biotin. In ABC-immunoperoxidase, ABC stands for Avidin-Biotin Complex. The biotinylated secondary antibody binds to the primary antibody that’s attached to the antigen, and the ABC reagent, which carries horseradish peroxidase via the avidin component, binds to the biotin on that secondary antibody. Avidin has multiple biotin-binding sites, which helps bring in more enzyme at the site, boosting the color development when the substrate is added. So the acronym specifically reflects this avidin–biotin interaction driving enzyme delivery and signal amplification. The other options don’t fit because the method relies on avidin binding to biotin, not on an antibody–biotin complex, nor on anything related to alkaline or autoclave in the name.