Endogenous biotin artifact is common in certain tissues such as in the cytoplasm of hepatocytes, proximal tubules in the kidney, and some tumors to name a few. When using an avidin-biotin detection system, along with heat-induced epitope retrieval (HIER), one should be aware of false-positive results that endogenous biotin and avidin can produce. To prevent this, an avidin-biotin blocking step should be used before the primary antibody incubation. Publications have suggested that an avidin-biotin blocking step should be used in every case that uses HIER regardless of the tissue.
A suggested blocking procedure is:
0.01% to 0.1% avidin followed by 0.001% to 0.01% biotin prior to the staining protocol
