Nonspecific background staining is a common problem with IHC staining. This can be attributed to the binding of staining reagents with endogenous avidin, endogenous biotin, and endogenous enzymes throughout the body.
Endogenous biotin is bound to many types of tissues. It is exceptionally high in brain, kidney, and liver concentration. Endogenous peroxidase is present in leukocytes, erythrocytes, and kidney and liver tissue. Endogenous alkaline phosphatase can be found in the intestine, kidney, lymphoid tissue, and placenta tissue.
This non-specific binding to endogenous substances must be blocked to enhance staining, reduce nonspecific staining, and avoid false-positive staining results. Blocking methods utilize unlabeled avidin-biotin, serum, and enzyme-quenching chemicals.
