Home › Microscopy & Imaging › Immunohistochemistry Protocol for Paraffin embedded Tissue Sections

Steps

1 Sample Preparation and Deparaffinization/Rehydration 01:39
2 Antigen Unmasking 02:45
3 Chromogenic Staining 03:48

Microscopy & Imaging Cell Signaling Technology

Immunohistochemistry Protocol for Paraffin embedded Tissue Sections

Protocol

IHC on paraffin-embedded tissue sections: deparaffinization, antigen retrieval, peroxidase blocking, primary and secondary antibody incubation, DAB detection, and counterstaining.

Difficulty

intermediate

Total time

6-8 hours (or overnight)

Biosafety

BSL-1

Steps

1

Sample Preparation and Deparaffinization/Rehydration

Bake slides at 60 C for 1 hour to melt paraffin. Pass slides through xylene (3 x 5 min) to remove paraffin, then graded ethanol (100%, 95%, 70%) and water to rehydrate the tissue for downstream staining.

▶ 01:39

2

Antigen Unmasking

Restore epitopes masked by formalin fixation: heat slides in citrate buffer (pH 6) or EDTA buffer (pH 9) at near-boiling for 10-20 min using a steamer or pressure cooker; cool slowly to room temperature.

▶ 02:45

3

Chromogenic Staining

Block endogenous peroxidase (3% H2O2, 10 min) and non-specific binding (normal serum). Apply primary antibody overnight at 4 C; wash with TBST; apply HRP-conjugated secondary antibody (30 min); develop with DAB substrate until brown signal appears. Counterstain nuclei with hematoxylin, dehydrate, and mount.

▶ 03:48

🚨 Failure Case Library (23) + Submit your own case

False negative — no staining at all

Even the positive control shows no staining; expected positive regions are completely blank; the experiment failed.

💡 4 · ✓ 4

Tissue detachment / sections fall off the slide

Tissue falls off during staining; sections become broken or missing; results cannot be interpreted.

💡 4 · ✓ 4

Abnormal nuclear staining (wrong subcellular localization)

Cell nuclei show strong staining when they shouldn't, or expected positive nuclei show no staining; nuclear/cytoplasmic localization is wrong.

💡 4 · ✓ 4

High Background from Insufficient Non-Specific Blocking

Diffuse background staining observed throughout tissue sections in IHC experiments, indicating inadequate blocking of non-specific antibody binding sites.

💡 4 · ✓ 4

High Background from Excessive Antibody Concentrations

Elevated background staining throughout tissue sections due to excessively high concentrations of primary or secondary antibodies leading to non-specific binding.

💡 4 · ✓ 5

Complete absence of IHC signal due to reagent degradation

No staining is observed in immunohistochemistry despite proper protocol execution. Previously validated antibodies or detection kits fail to produce any signal.

💡 4 · ✓ 6

Incorrect Antibody Diluent Selection

Suboptimal signal intensity or background issues despite correct antibody concentration. Different antibodies show dramatically different performance in TBST/5% NGS versus SignalStain Antibody Diluent.

💡 3 · ✓ 3

Mouse-on-Mouse (MOM) Background

High background staining when using mouse primary antibody on mouse tissue. Secondary antibody binds endogenous mouse IgG throughout the tissue, creating non-specific signal.

💡 3 · ✓ 4

Strong positive background / non-specific staining

Whole slide appears brown/diffuse stained; negative control also shows signal; impossible to distinguish true positive signal.

💡 5 · ✓ 5

Weak staining / signal too faint

Positive regions show very pale staining; barely distinguishable from negative control; signal appears dotted or discontinuous.

💡 5 · ✓ 5

Formaldehyde fixation masked epitopes preventing antibody binding

No staining in formaldehyde-fixed tissues despite validated antibody. Fixation-induced protein crosslinking masks epitopes and prevents antibody recognition.

💡 4 · ✓ 5

Weak or Suboptimal IHC Staining Intensity

Staining signal is present but significantly weaker than expected, with poor contrast between positive cells and background, making interpretation difficult.

💡 5 · ✓ 5

Inadequate Detection System Sensitivity

Weak signal or no staining despite proper primary antibody performance. Standard HRP-conjugated secondary antibodies fail to provide sufficient signal amplification.

💡 4 · ✓ 4

Suboptimal Antigen Retrieval Method Selection

Weak or absent staining despite proper antibody concentration and incubation. Clear performance differences observed when comparing different antigen retrieval heating methods.

💡 4 · ✓ 4

Nuclear protein not detected due to insufficient permeabilization

No staining observed when targeting nuclear proteins. Antibody cannot access nuclear compartment despite proper antibody concentration and incubation time.

💡 3 · ✓ 4

FFPE tissue shows no staining from incomplete deparaffinization

Paraffin-embedded tissue sections show no immunostaining. Residual paraffin creates a physical barrier preventing antibody access to tissue antigens.

💡 3 · ✓ 4

Primary-secondary antibody incompatibility preventing detection

No signal detected despite proper primary antibody binding. Secondary antibody fails to recognize or bind to the primary antibody, breaking the detection chain.

💡 4 · ✓ 5

High Background Staining in IHC

Excessive background signal obscuring specific staining. Non-specific binding observed throughout tissue sections, making interpretation difficult.

💡 5 · ✓ 5

Incorrect Antibody Diluent Selection

Staining quality is significantly reduced or inconsistent when using generic diluent instead of product-specific recommended diluent, as different antibodies perform optimally in different buffer compositions.

💡 3 · ✓ 4

Inadequate Washing Steps Causing Poor Contrast

High background persists with poor contrast between positive signal and background despite other optimization steps, making interpretation difficult.

💡 4 · ✓ 4

Endogenous Biotin Interference

High background staining specifically in kidney, liver, or other biotin-rich tissues when using biotin-based detection. Background not resolved by standard blocking procedures.

💡 3 · ✓ 3

Edge effect / uneven staining across the slide

Slide edges show darker staining than center, or one half stains more than the other; reproducibility between fields is poor.

💡 4 · ✓ 4

Suboptimal Primary Antibody Incubation

Inconsistent or weak staining results despite following protocol. Staining intensity varies between experiments using same antibody lot and tissue type.

💡 3 · ✓ 3

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