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 found throughout the body.
Endogenous biotin is bound to many types of tissues. It is particularly high in concentration in the brain, kidney, and liver. Endogenous peroxidase is present in leukocytes, erythrocytes, as well as 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 include those that utilize unlabeled avidin-biotin, serum, and enzyme-quenching chemicals.
