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STAT3 / Signal transducer and activator of transcription 3 · IHC design guide
Design Immunohistochemistry for STAT3
Plan STAT3 staining and scoring in paraffin sections using the variable cytoplasmic and nuclear tissue pattern (HPA tissue IHC). Placental cytotrophoblasts provide a high-staining reference (HPA tissue IHC); score nuclear and cytoplasmic staining separately because LIF can shift STAT3 into nuclei (UniProt).
Evidence assembled Oct 2026 · For research use; verify linked source records and product datasheet before use
STAT3 Immunohistochemistry Experimental Design Guide
Expected localisation, validated protocols, controls and antibodies — the at-a-glance facts below, then the full design guide.
Must know before staining
| Expected localisation | Variable cytoplasmic and nuclear staining (HPA tissue IHC) | |
| Staining pattern | Cytotrophoblasts stain strongly; compartments vary (HPA tissue IHC) | |
| Antigen retrieval | Tris-EDTA pH 9.0 HIER, 95–98 °C, 20 min (rule: nuclear antigen) | |
| Positive control | Placenta+4 more · see all | |
| Negative control | Heart muscle+3 more · see all |
Important caveats
Reasons your staining may differ from the expected pattern.
| Fixation | Keep fixation consistent across paraffin sections. (standard IHC practice; not target-specific) | |
| Caveat | Nuclear staining alone does not prove Tyr705 activation (UniProt) | |
| Regulation | LIF promotes nuclear accumulation (UniProt) | |
| Isoform / epitope | 3 isoforms; check epitope coverage across variants (UniProt) |
Section 1
Recommended STAT3 IHC & IF Protocols
The catalog antibody protocol is followed by four published STAT3 IHC protocols, including phospho-STAT3 staining in kidney, lung, glioblastoma and salivary gland samples (PMC7114280; PMC5374098; PMC6829927; PMC4287356).
| Sample | Paraffin-embedded tissue sections; fixative not specified (datasheet M00007-1; sample unspecified) |
| Fixation | Image fixative and duration unreported (datasheet M00007-1); verify before use. |
| Sectioning | 4–5 µm sections on charged slides (standard) |
| Deparaffinisation | Xylene, graded ethanol series to water (standard) |
| Antigen retrieval | Heat-induced epitope retrieval in Tris-EDTA buffer, pH 9.0, 20 min at 95–98 °C (standard rule: nuclear antigen) |
| Peroxidase block | 3% H2O2, 10 min, room temperature (standard) |
| Blocking | 10% normal serum of the secondary host, 30 min, room temperature (standard) |
| Primary antibody | Rabbit monoclonal (clone CAB-19) anti-STAT3, 1:50-1:200 (datasheet M00007-1) |
| Primary incubation | Overnight at 4 °C (standard) |
| Detection | HRP-polymer secondary, DAB chromogen 5–10 min (standard) |
| Counterstain | Hematoxylin, blue, dehydrate and mount (standard) |
| Expected result | STAT3-positive staining in cytotrophoblasts of placenta (HPA tissue IHC: High). HPA tissue profile: General cytoplasmic and nuclear expression at variable levels. No signal in the no-primary control. |
💡Decision noteStart with pH 9.0 Tris-EDTA retrieval at 95–98 °C for 20 min (page retrieval); optimize separately when staining phospho-STAT3.
Section 2
What Is the Expected STAT3 Staining Pattern?
STAT3 stains cytoplasm/nuclei in cytotrophoblasts (HPA: High, Supported); lacks a TM segment (UniProt P40763).
| Cytoplasmic and nuclear stain in cytotrophoblasts (HPA: High) | Expected distribution (HPA: tissue IHC); nuclear enrichment can vary with signaling (UniProt P40763). |
| Membrane-only staining | Suspect artefact; STAT3 has no TM segment (UniProt P40763). |
| Strong stain in prostate glandular cells | Unexpected; check cross-reactivity or endogenous detection activity (HPA: Not detected; general IHC practice). |
| Diffuse stain across cells and stroma | Background may reflect incomplete blocking or excess primary antibody (general IHC practice). |
| No stain in placental cytotrophoblasts | Unexpected for a positive control; assess retrieval and detection (HPA: High; general IHC practice). |
💡Expected STAT3 appearanceCytotrophoblasts: high cytoplasmic/nuclear stain (HPA: High); membrane-only is suspect (UniProt: no TM).
| Signaling state (UniProt P40763) | Usually cytoplasmic without stimuli; nuclear STAT3 can increase after activation (UniProt P40763). |
| Tissue context (HPA: tissue IHC) | Cytotrophoblasts are High; adipocytes are Medium; prostate glandular cells are Not detected (HPA). |
| Antibody choice (HPA: antibody data) | Five listed antibodies have IHC Supported status (HPA: antibody data). |
| IF/ICC: expected location? | Nucleoplasm and cytosol (HPA: ICC-IF); follow the separate IF/ICC guide for method. |
| Situation | Likely cause | Next action |
|---|---|---|
| No cytotrophoblast signal (HPA: High) | Retrieval or detection failure is possible (general IHC practice). | Check the positive control, retrieval and detection steps (general IHC practice). |
| Diffuse section background | Incomplete blocking or excess primary antibody is possible (general IHC practice). | Use a no-primary control; adjust blocking or dilution (general IHC practice). |
| Membrane-only signal | Localization conflicts with STAT3 topology (UniProt P40763: no TM). | Check staining controls and antibody specificity (general IHC practice). |
| Prostate glandular cells stain strongly | Unexpected signal (HPA: Not detected in prostate glandular cells). | Check controls; compare another IHC Supported antibody (HPA: antibody data). |
| No nuclear enrichment after stimulation | A signaling-dependent shift may be absent (UniProt P40763). | Verify the stimulus and score nuclei with a counterstain (general IHC practice). |
Experiment evidence
IHC & IF images showing STAT3 staining
M00007-1 · IHCImmunohistochemical analysis of paraffin-embedded Human Hodgkin's lymphoma, using the Antibody at 1:50 dilution.
M00007-1 · IHCImmunohistochemical analysis of paraffin-embedded Human astrocytoma, using the Antibody at 1:50 dilution.
M00007-1 · IFImmunofluorescent analysis of Hela cells treated with IFNalpha, using STAT3 Antibody.
A00007-1 · IHCImmunohistochemistry of STAT3 in human small intestine tissue with STAT3 antibody at 5 μg/ml.
A00007-1 · IFImmunofluorescence of STAT3 in human small intestine tissue with STAT3 antibody at 20 μg/ml.
M00007 · IHCImmunohistochemical analysis of paraffin-embedded human thyroid carcinoma, using STAT3 Antibody.
M00007 · IFImmunofluorescent analysis of HeLa cells, using STAT3 Antibody.
M00007-2 · IHCImmunohistochemical analysis of paraffin-embedded mouse liver, using STAT3 Antibody.
M00007-2 · IFImmunofluorescent analysis of Hela cells, using STAT3 Antibody .
M00007-4 · IHCHuman pancreas was stained with anti-STAT3 rabbit antibody
P00007-1 · IHCImmunohistochemical analysis of paraffin-embedded rat brain, using Phospho-STAT3 (S727) Antibody.
P00007-1 · IFIF analysis of STAT3 using anti-STAT3 antibody (P00007-1). STAT3 was detected in immunocytochemical section of Hela cell. Enzyme antigen ret
PB9511 · IHC
PB9511 · IFIF analysis of STAT3 using anti-STAT3 antibody (PB9511) and anti-Beta Tubulin antibody (M01857-3). STAT3 was detected in immunocytochemical
HPA · Cerebral cortexHuman Protein Atlas IHC, Cerebral cortex. Source: https://www.proteinatlas.org/ENSG00000168610-STAT3/tissue/cerebral+cortex#imid_18953034
HPA · LungHuman Protein Atlas IHC, Lung. Source: https://www.proteinatlas.org/ENSG00000168610-STAT3/tissue/lung#imid_18914996
HPA · ColonHuman Protein Atlas IHC, Colon. Source: https://www.proteinatlas.org/ENSG00000168610-STAT3/tissue/colon#imid_18915027
HPA · LiverHuman Protein Atlas IHC, Liver. Source: https://www.proteinatlas.org/ENSG00000168610-STAT3/tissue/liver#imid_18915842
HPA · ICC-IF A-431Human Protein Atlas immunofluorescence, A-431, antibody HPA001671; green = STAT3, blue = nucleus, red = microtubules.
HPA · ICC-IF A-431Human Protein Atlas immunofluorescence, A-431, antibody HPA001671; green = STAT3, blue = nucleus, red = microtubules.
← swipe / scroll for more images →
Real IHC / IF data behind the staining-pattern expectations in this section.
Sample controls for STAT3 IHC & IF
🧪Run placenta first and score cytotrophoblasts, where STAT3 staining is High (HPA: High in placental cytotrophoblasts). Use parathyroid glandular cells as the negative tissue (HPA: Not detected in parathyroid glandular cells); on the placenta slide, cells outside the cytotrophoblast compartment should show only background where they lack detectable STAT3, but the supplied HPA row does not identify a specific internal negative cell type (HPA: placental cytotrophoblast row).
Positive control tissue: Placenta (Cytotrophoblasts, HPA High)
Negative control tissue: Heart muscle (HPA Not detected)
ICC-IF cell lines (HPA subcellular resource): HPA ICC-IF images show STAT3 in A-431, U-251MG, U2OS, SK-MEL-30, SiHa, with annotated localisation: Nucleoplasm (enhanced), Cytosol (enhanced) (HPA subcellular).
Technical controls: Include a no-primary, secondary-only control; use host- and immunoglobulin-matched control antibody for a monoclonal primary or matched nonimmune immunoglobulin for a polyclonal primary; and, where available, compare with a STAT3-knockout specimen processed the same way (standard IHC practice). For chromogenic placenta IHC, quench endogenous peroxidase and block endogenous biotin if using avidin–biotin detection (standard IHC practice).
⚠️Feasibility: A STAT3-specific fixation window, fixation effect, and retrieval dependency are unreported in the supplied target and application evidence; establish antigen retrieval using the catalog antibody’s IHC-P protocol and appropriate controls (supplied evidence; standard IHC practice). The selected paraffin-section caption gives a 1:50 dilution for Hodgkin’s lymphoma tissue but leaves the fixative unreported, so it does not establish fixation (selected tissue-IHC caption). The evidence does not establish whether frozen-section IHC or IF is easier for STAT3; in placenta, assess background from endogenous peroxidase and, if applicable, endogenous biotin (supplied evidence; standard IHC practice). The selected M00007-1 tissue-IHC caption documents paraffin sections, but does not specify the fixative (selected-SKU IHC image M00007-1).
HPA tissue IHC evidence for STAT3
Comprehensive Human Protein Atlas IHC scoring per tissue (reliability: Supported — Medium consistency between antibody staining and RNA expression data.). Rows are taken directly from the HPA tissue chart — click any row's HPA link to view the source.
Positive expression · recommended positive controls
| Tissue | Cell type | Level | Evidence | Source |
|---|---|---|---|---|
| Placenta | Cytotrophoblasts | High | Protein (IHC) | HPA → |
| Adipose tissue | Adipocytes | Medium | Protein (IHC) | HPA → |
| Adrenal gland | Glandular cells | Medium | Protein (IHC) | HPA → |
| Appendix | Glandular cells | Medium | Protein (IHC) | HPA → |
| Breast | Adipocytes | Medium | Protein (IHC) | HPA → |
Undetected expression · recommended negative controls
| Tissue | Cell type | Level | Evidence | Source |
|---|---|---|---|---|
| Heart muscle | Cardiomyocytes | Not detected | Protein (IHC) | HPA → |
| Hippocampus | Glial cells | Not detected | Protein (IHC) | HPA → |
| Parathyroid gland | Glandular cells | Not detected | Protein (IHC) | HPA → |
| Prostate | Glandular cells | Not detected | Protein (IHC) | HPA → |
Section 3
Advanced STAT3 IHC Tips
Troubleshoot STAT3 staining by checking retrieval, cell identity, and nuclear versus cytoplasmic signal before comparing chromogenic scores across sections.
How should I optimize retrieval when STAT3 staining is weak in paraffin sections?
Use Tris-EDTA pH 9.0 heat-induced retrieval at 95–98 °C for 20 min first (page retrieval setting: nuclear antigen). Run a known positive section alongside the test section, and keep section thickness, cooling, and detection conditions matched (standard IHC practice); cytotrophoblasts are a documented high-staining reference population (HPA: High in placental cytotrophoblasts). If staining remains weak, compare a milder retrieval condition on adjacent sections while checking for tissue damage and background (standard IHC practice). Score nuclear and cytoplasmic staining separately, because STAT3 occupies both compartments and can move into the nucleus after signaling (UniProt P40763 localisation).
Could fixation explain weak or uneven STAT3 staining?
The selected STAT3 image documents paraffin-embedded Hodgkin’s lymphoma stained at 1:50, but its caption does not report a fixative (catalog caption: M00007-1). Target-specific fixation sensitivity is therefore unknown; do not assign a particular fixation time or fixative as the cause of weak STAT3 staining from this evidence (catalog caption: M00007-1). Check fixation records and compare sections processed together, then inspect morphology before changing retrieval or antibody concentration (standard IHC practice). Include a reference section in each run and keep processing, retrieval, and detection consistent so a staining difference can be evaluated against the technical controls (standard IHC practice).
Should STAT3 appear in nuclei, cytoplasm, or both?
Expect variable nuclear and cytoplasmic staining in tissue sections (HPA: general cytoplasmic and nuclear expression); STAT3 is predominantly cytoplasmic without stimuli and can accumulate in nuclei after signaling (UniProt P40763 localisation). Score the two compartments independently instead of treating every stained cell as evidence of nuclear activation (standard IHC practice). Review individual cell boundaries at high magnification, because crowded nuclei and diffuse chromogen can make cytoplasmic staining appear nuclear (standard IHC practice). A nuclear signal is biologically plausible, but constitutive nuclear STAT3 can occur independently of tyrosine phosphorylation, so localisation alone cannot establish phosphorylation status (UniProt P40763 localisation).
How do STAT3 isoforms and epitope uncertainty affect IHC interpretation?
STAT3 has 3 listed isoforms, including isoform 1, Del-701, and isoform 3 (UniProt P40763 isoforms). The supplied caption does not identify the M00007-1 epitope, so staining cannot be assigned to a specific isoform or modification from this image alone (catalog caption: M00007-1). STAT3 also has a defined SH2 domain at residues 580–670 and multiple modified residues (UniProt P40763 domains and modified residues), which makes epitope documentation relevant when comparing antibodies. Check the antibody’s stated immunogen or epitope before making isoform claims, and interpret a change in staining as a change in detected antigen rather than a specific splice variant unless specificity has been established (standard IHC practice).
How can I check STAT3 localisation by multiplex immunofluorescence?
Pair STAT3 with an independently validated marker for the expected cell population, such as a cytotrophoblast identity marker when examining placenta (HPA: High in placental cytotrophoblasts; standard IF practice). Choose spectrally separated fluorophores and place the weaker signal in a channel with low tissue autofluorescence, checking single-stain and unstained controls before interpreting overlap (standard IF practice). Permeabilise sufficiently for access to cytosolic and nuclear epitopes, then verify that cell boundaries and nuclear counterstain remain clear (UniProt P40763 localisation; standard IF practice). STAT3 has no transmembrane segment, so the relevant access question is intracellular staining rather than an extracellular membrane epitope (UniProt P40763 topology).
What should I adjust if chromogenic STAT3 staining is diffuse?
First compare the test section with a no-primary control and inspect whether chromogen appears over tissue structures rather than within identifiable cells (standard IHC practice). Block endogenous peroxidase for peroxidase-based detection, use an appropriate protein block, and wash consistently before DAB development (standard IHC practice). Titrate the catalog antibody around the documented 1:50 image condition only as an optimization starting point; the caption reports that dilution for paraffin-embedded Hodgkin’s lymphoma, not a universal optimum (catalog caption: M00007-1). If background rises with stronger retrieval or longer DAB exposure, adjust those steps while retaining a positive reference section (standard IHC practice).
How should I quantify STAT3 staining across paraffin sections? ⚠ ANSWER MARKED FOR VERIFICATION
Define the cell population and region of interest before scoring, then record nuclear and cytoplasmic STAT3 separately (HPA: variable cytoplasmic and nuclear expression; standard IHC practice). For intensity scoring, use an H-score based on the percentage of cells at each intensity; for prevalence, report the percentage of positive cells or positive-cell density per mm² (standard IHC practice). Normalise counts to the number of evaluable cells or the measured tissue area, and apply the same threshold, counterstain, and imaging settings across samples (standard IHC practice). Exclude folds, necrosis, and section edges from the denominator using prespecified rules (standard IHC practice).
When is an apparent STAT3-positive area likely to be artefact?
Treat a signal as credible when it lies within identifiable cells, matches an interpretable nuclear or cytoplasmic compartment, and recurs in a suitable reference section (HPA: cytoplasmic and nuclear expression; standard IHC practice). Recheck staining confined to cut edges, folds, or necrotic areas, where section artefacts can distort chromogenic interpretation (standard IHC practice). Confirm the stained cell type before comparing samples: placental cytotrophoblasts are reported High, while cardiomyocytes in heart muscle are reported Not detected in the cited tissue profile (HPA: tissue IHC). Signal persisting in a no-primary control warrants investigation of endogenous enzyme activity or detection background before assigning it to STAT3 (standard IHC practice).
Boster reagents
Best STAT3 / Signal transducer and activator of transcription 3 IHC Antibodies
The catalog lists IHC and IF applications for STAT3 and phospho-STAT3 antibodies (catalog applications), with IHC images from human tissues, mouse liver, and rat brain (catalog IHC captions).
Real IHC data
Anti-STAT3 Rabbit Monoclonal Antibody
Cat # M00007-1
Real IHC data
Anti-STAT3 Antibody
Cat # A00007-1
Real IHC data
Anti-STAT3 Rabbit Monoclonal Antibody
Cat # M00007
Real IHC data
Anti-STAT3 Rabbit Monoclonal Antibody
Cat # M00007-2
Real IHC data
Anti-STAT3 Rabbit Monoclonal Antibody
Cat # M00007-4
Real IHC data
Anti-Phospho-STAT3 (S727) Rabbit Monoclonal Antibody
Cat # P00007-1
M00007-1 shows IHC in human Hodgkin’s lymphoma (catalog M00007-1 IHC caption), A00007-1 in human small intestine (catalog A00007-1 IHC caption), and M00007 in human thyroid carcinoma (catalog M00007 IHC caption). M00007-2 shows mouse liver (catalog M00007-2 IHC caption), M00007-4 shows human pancreas (catalog M00007-4 IHC caption), and phospho-STAT3 (S727) P00007-1 shows rat brain (catalog P00007-1 IHC caption).
Which to pick: For paraffin-section IHC, M00007-1 is a rabbit monoclonal with an IHC image of paraffin-embedded human Hodgkin’s lymphoma at 1:50 (catalog M00007-1 title and IHC caption). For IF/ICC, M00007 lists both applications and has a HeLa IF image (catalog M00007 applications and IF caption). For cross-species IHC, M00007-1 lists human, mouse, and rat reactivity and has human and rat IHC images; the listed mouse reactivity lacks a mouse IHC image for this SKU, and its paraffin-section caption does not report the fixative (catalog M00007-1 reactivity and IHC captions).
Each figure is that product's own IHC / IF validation image from its datasheet.
References
- UniProt Consortium. UniProt entry P40763 (STAT3_HUMAN, Signal transducer and activator of transcription 3).
- Human Protein Atlas. STAT3 tissue IHC expression (reliability: Supported).
- Human Protein Atlas. STAT3 subcellular location (ICC-IF): Localized to the nucleoplasm and cytosol..
- Human Protein Atlas. STAT3 antibody validation summary (6 antibodies).
- Saturated hydrogen alleviates CCl(4)-induced acute kidney injury via JAK2/STAT3/p65 signaling. The Journal of international medical research 2020 — PMC7114280.
- Significance of Stat3 Signaling in Epithelial Cell Differentiation of Fetal Mouse Lungs. Acta histochemica et cytochemica 2017 — PMC5374098.
- The role of p-Stat3 Y705 immunohistochemistry in glioblastoma prognosis. Diagnostic pathology 2019 — PMC6829927.
- Immunohistochemical expression of the oncogenic molecules active Stat3 and survivin in benign and malignant salivary gland tumors. Oral surgery, oral medicine, oral pathology, oral radiology, and endodontics 2009 — PMC4287356.
- PubMed PMID:7512451 — UniProt-cited evidence.
- PubMed PMID:9630560 — UniProt-cited evidence.
- PubMed PMID:14702039 — UniProt-cited evidence.
Immunohistochemistry protocol sheet for STAT3 (Signal transducer and activator of transcription 3). Expected localisation Variable cytoplasmic and nuclear staining (HPA tissue IHC). Antigen retrieval: Tris-EDTA pH 9.0 HIER, 95–98 °C, 20 min (rule: nuclear antigen). Validated IHC antibody: M00007-1 at 1:50-1:200 (the product's own IHC validation image is shown). Controls (HPA): positive Placenta (Cytotrophoblasts); negative Heart muscle. IHC workflow; specimen preparation unspecified. Protocol steps: 1. Sample: Paraffin-embedded tissue sections; fixative not specified (datasheet M00007-1; sample unspecified); 2. Fixation: Image fixative and duration unreported (datasheet M00007-1); verify before use.; 3. Sectioning: 4–5 µm sections on charged slides (standard); 4. Deparaffinisation: Xylene, graded ethanol series to water (standard); 5. Antigen retrieval: Heat-induced epitope retrieval in Tris-EDTA buffer, pH 9.0 , 20 min at 95–98 °C…; 6. Peroxidase block: 3% H2O2, 10 min , room temperature (standard); 7. Blocking: 10% normal serum of the secondary host, 30 min , room temperature (standard); 8. Primary antibody: Rabbit monoclonal (clone CAB-19) anti-STAT3, 1:50-1:200 (datasheet M00007-1); 9. Primary incubation: Overnight at 4 °C (standard). Watch for: Fixation: Keep fixation consistent across paraffin sections. (standard IHC practice; not target-specific); Caveat: Nuclear staining alone does not prove Tyr705 activation (UniProt); Isoform / epitope: 3 isoforms; check epitope coverage across variants (UniProt); Regulation: LIF promotes nuclear accumulation (UniProt). Evidence: UniProt P40763, HPA tissue IHC · Supported, HPA ICC-IF · nucleoplasm and cytosol., Datasheet M00007-1, PMC7114280, PMC5374098. QR code links to https://www.bosterbio.com/bosterbio-gene-info-cards/STAT3/immunohistochemistry-ihc-guide.