High Background Staining in IHC (Immunohistochemistry (CST Guide))

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Excessive background signal obscuring specific staining. Non-specific binding observed throughout tissue sections, making interpretation difficult. Common causes: 1) Inadequate deparaffinization causing spotty, uneven background 2) Endogenous peroxidase activity in tissues producing excess background with HRP-based detection 3) Insufficient blocking (less than 30 minutes or improper blocking buffer) 4) Inadequate washing between antibody incubations (fewer than 3×5 min washes with TBST) 5) Antibody concentration too high for the specific tissue or detection system Solutions: 1) Repeat experiment with new tissue sections using fresh xylene for complete deparaffinization 2) Quench endogenous peroxidase: incubate slides in 3% H₂O₂ (diluted in RODI water) for 10 minutes prior to primary antibody 3) Ensure adequate blocking: use 1X TBST #9997 with 5% Normal Goat Serum #5425 for 30 minutes before primary antibody 4) Wash slides 3 times for 5 minutes with TBST #9997 after both primary and secondary antibody incubations 5) Titrate antibody to lower concentration; follow product datasheet recommendations for dilution