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The page below is a sample from the LabCE course Immunohistochemistry (IHC) Basics in Histology. Access the complete course and earn ASCLS P.A.C.E.-approved continuing education credits by subscribing online.

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Avidin/Biotin Blocking

Endogenous biotin artifact is common in certain tissues such as in the cytoplasm of hepatocytes, proximal tubules in the kidney, brain tissue and in some tumors. When using an avidin-biotin detection system and especially when combined 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. Blocking is achieved by applying unlabeled avidin followed by an application of unlabeled biotin. Publications have suggested that an avidin-biotin blocking step should be used in every case that uses HIER regardless of the tissue being stained.
A suggested blocking procedure is:
0.01% to 0.1% avidin followed by 0.001% to 0.01% biotin prior to the staining protocol