These kits were developed to prevent non-specific binding of avidin or streptavidin based detection reagents primarily to endogenous biotin in cell and tissue IHC and IF applications. It is generally recommended to match the blocking and detection reagent such as using an avidin/biotin blocking kit with an avidin based detection system. In most cases, however, these kits can be used interchangeably, except in circumstances where avidin or streptavidin may bind to inherent non-biotin associated structures (see: Alon, R., et al {1992}, Eur. J. Cell Biol. 58:271-279).

If the primary antibody is unconjugated, then the avidin/biotin blocking kit reagents can be applied at any time prior to the application of the biotinylated secondary antibody. If the primary antibody is biotinylated, then we would recommend applying the avidin/biotin blocking kit reagents before primary antibody incubation.