Practice question

Signal amplification without compromising antigen recognition can be achieved through biotin-streptavidin chemistry. Secondary antibody conjugated to biotin retains full binding specificity for primary antibody Fc region, but each biotin can recruit tetrameric avidin coupled to multiple enzyme molecules. This creates a lattice multiplying enzyme copies per immune complex, boosting substrate conversion and lowering detection limit. Because primary antigen-antibody affinity remains unchanged, background does not rise appreciably. Simply adding more antigen, using unlabeled antibody or increasing substrate alone cannot produce equivalent enhancement and may elevate nonspecific interactions or exhaust kinetics.