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IRF1 / Interferon regulatory factor 1 · IHC design guide
Design Immunohistochemistry for IRF1
Plan chromogenic IRF1 IHC on paraffin sections using the catalog antibody at 0.5–1 μg/mL (datasheet A00580-1). Assess nuclear and nucleolar staining against tissue examples, while accounting for medium consistency between antibody staining and RNA expression (HPA tissue IHC).
Evidence assembled Oct 2026 · For research use; verify linked source records and product datasheet before use
IRF1 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 | Nuclear and nucleolar tissue staining (HPA tissue IHC) | |
| Staining pattern | Nuclear and nucleolar; high in placental endothelial cells (HPA tissue IHC) | |
| Antigen retrieval | EDTA pH 8.0 HIER, heat-mediated (datasheet A00580-1) | |
| Positive control | Placenta+4 more · see all | |
| Negative control | Cerebellum+4 more · see all |
Important caveats
Reasons your staining may differ from the expected pattern.
| Fixation | Keep fixation consistent across sections (standard IHC practice; not target-specific) | |
| Caveat | Antibody staining and RNA show medium consistency (HPA tissue IHC) | |
| Regulation | Staining intensity varies by tissue cell type (HPA tissue IHC) | |
| Isoform / epitope | No annotated isoforms; one 1–325 chain (UniProt) |
Section 1
Recommended IRF1 IHC & IF Protocols
Compare the catalog antibody’s IHC protocol (datasheet A00580-1) with three published IRF1 IHC protocols (PMC4359953; PMC13472745; PMC12799679).
| Sample | Paraffin-embedded human Lung cancer tissue; fixative not specified (datasheet A00580-1) |
| Fixation | Image fixative and duration unreported (datasheet A00580-1); verify before use. |
| Sectioning | 4–5 µm sections on charged slides (standard) |
| Deparaffinisation | Xylene, graded ethanol series to water (standard) |
| Antigen retrieval | Heat retrieval: EDTA pH 8.0 (datasheet A00580-1); 20 min, 95–100 °C (standard) |
| Peroxidase block | 3% H2O2, 10 min, room temperature (standard) |
| Blocking | 10% goat serum (datasheet A00580-1) |
| Primary antibody | Rabbit anti-IRF1, 0.5-1μg/ml (datasheet A00580-1) |
| Primary incubation | Overnight at 4 °C (datasheet A00580-1) |
| Detection | Streptavidin-biotin complex (SABC), DAB chromogen (datasheet A00580-1) |
| Counterstain | Hematoxylin, blue, dehydrate and mount (standard) |
| Expected result | IRF1-positive staining in endothelial cells of placenta (HPA tissue IHC: High). HPA tissue profile: Nuclear and nucleolar expression in several different tissue types. No signal in the no-primary control. |
💡Decision noteStart with heat-mediated EDTA pH 8.0 retrieval for the catalog antibody (datasheet A00580-1). Optimize retrieval when adapting a published protocol.
Section 2
What Is the Expected IRF1 Staining Pattern?
IRF1 should appear chiefly in nuclei, sometimes with nucleolar staining, across several tissue types (HPA tissue IHC: Supported). Cytoplasmic signal can also occur (UniProt P10914; HPA ICC-IF). Placental endothelial cells and testicular pachytene spermatocytes are high-staining examples (HPA tissue IHC: High). IRF1 has no transmembrane segment, so a membrane-restricted pattern is unexpected (UniProt P10914 topology).
| Distinct nuclear staining in placental endothelial cells or testicular pachytene spermatocytes. | This matches high-staining cell populations in the tissue survey (HPA tissue IHC: High). Nuclear staining also fits the reported tissue profile (HPA tissue IHC: nuclear and nucleolar). Compare the named cells with surrounding cells; the tissue label alone does not identify every cell as positive (HPA tissue IHC: cell-specific levels). |
| Signal is restricted to cell membranes, or a known-positive population shows cytoplasm without discernible nuclei. | Review the pattern before scoring it as IRF1: the protein has no transmembrane segment (UniProt P10914 topology), while nuclear localisation is expected (HPA tissue IHC). Cytoplasmic localisation is possible (UniProt P10914; HPA ICC-IF), so cytoplasmic signal alone is not proof of artefact. |
| Strong staining appears in a listed non-detected cell population, such as liver cholangiocytes. | This conflicts with that population's surveyed result (HPA tissue IHC: cholangiocytes Not detected). Check morphology and controls for cross-reactivity or endogenous detection activity (standard IHC practice). One unexpected field cannot establish a universal negative result: HPA reports staining at the named cell level (HPA tissue IHC). |
| Brown deposit spreads across the section without clear cellular boundaries or a nuclear pattern. | Treat the diffuse appearance as possible background rather than assigning it to IRF1-positive cells (standard IHC practice). Compare with a detection control and inspect whether the expected nuclei remain distinguishable (standard IHC practice; HPA tissue IHC: nuclear profile). |
| A known high-staining population has no detectable nuclear signal. | First verify the selected cells and control section: placental endothelial cells and pachytene spermatocytes are high in the survey (HPA tissue IHC: High). A blank result may reflect the assay workflow or specimen; the supplied sources do not establish an IRF1-specific fixation sensitivity. |
💡Expected IRF1 appearanceCall the stain positive when identifiable placental endothelial cells or testicular pachytene spermatocytes show strong, predominantly nuclear signal, potentially nucleolar (HPA tissue IHC: High; nuclear and nucleolar); isolated membrane staining is suspect (UniProt P10914 topology), and diffuse deposit is background until controls resolve it (standard IHC practice).
| Compartment and scoring | Score nuclei in identified cells first because tissue IHC reports nuclear and nucleolar expression (HPA tissue IHC). Cytoplasmic staining can accompany it (UniProt P10914; HPA ICC-IF). An apparent shift in the nuclear-to-cytoplasmic balance needs cautious interpretation: MYD88-associated IRF1 enters nuclei more efficiently (UniProt P10914), but the supplied tissue survey does not measure that interaction. |
| Cell population within a tissue | Choose and score the named population: placental endothelial cells and testicular pachytene spermatocytes are High, while liver cholangiocytes and lymph-node germinal-center cells are Not detected (HPA tissue IHC). A positive or negative whole-tissue label would obscure these cell-specific observations (HPA tissue IHC). |
| RNA and protein readouts | Bone marrow is tissue-enhanced by RNA yet its hematopoietic cells show Low protein staining in this survey (HPA tissue IHC). Use the observed IHC level when choosing a staining reference; RNA enrichment does not set an expected chromogenic intensity (HPA tissue IHC: RNA specificity and protein levels). |
| Evidence strength and antibody choice | The tissue profile is Supported, with medium consistency between staining and RNA data (HPA tissue IHC: reliability). HPA063131 and CAB011662 have Supported IHC status; HPA070953 has no listed IHC status (HPA antibody validation). Those labels support cautious comparison across specimens, not a claim that every cell will stain identically. |
| IF/ICC Q: Should fluorescence reproduce the paraffin-section pattern? | A: Use compartment agreement as a check, not identical tissue intensity: ICC-IF places IRF1 mainly in nucleoplasm with additional cytosol (HPA ICC-IF: approved locations), whereas the tissue IHC profile includes nuclear and nucleolar staining (HPA tissue IHC). This section supplies no IF/ICC protocol option. |
| Situation | Likely cause | Next action |
|---|---|---|
| The positive control has no nuclear staining. | The selected control cells may be absent, or a general retrieval, primary-antibody, or detection step may have failed (standard IHC practice). IRF1-specific retrieval or fixation sensitivity is unreported in the supplied sources. | Confirm that placental endothelial cells or testicular pachytene spermatocytes are present (HPA tissue IHC: High). Then check the IHC-validated antibody's stated IHC-P instructions and run the workflow controls (standard IHC practice). |
| Only membranes carry a crisp chromogenic rim. | Membrane-restricted IRF1 conflicts with its lack of a transmembrane segment and reported nuclear distribution (UniProt P10914 topology; HPA tissue IHC). | Verify the stained structure against morphology and a detection control; score IRF1 only when a compatible cellular pattern is present (standard IHC practice; HPA tissue IHC: nuclear profile). |
| A surveyed non-detected population stains strongly. | Possible cross-reactivity, endogenous detection activity, or mistaken cell identification should be checked (standard IHC practice). For example, liver cholangiocytes were Not detected (HPA tissue IHC). | Reidentify the cells, inspect the detection control, and compare a named high-staining population on a separate control section (standard IHC practice; HPA tissue IHC: High in placental endothelial cells). |
| The entire section has diffuse brown haze. | Diffuse deposit can obscure the compartment needed to interpret IRF1 staining (standard IHC practice; HPA tissue IHC: nuclear profile). It does not establish widespread IRF1 expression. | Inspect reagent-only detection controls and the wash and blocking steps; rescore only cells with interpretable boundaries and nuclei (standard IHC practice). |
| Cytoplasm stains alongside nuclei. | This can be compatible with IRF1: UniProt lists nucleus and cytoplasm, and ICC-IF reports additional cytosol (UniProt P10914; HPA ICC-IF). | Record nuclear and cytoplasmic staining separately, checking that the expected nuclear signal is visible in the relevant cells (standard IHC scoring practice; HPA tissue IHC: nuclear profile). |
| Bone marrow looks faint despite its RNA enrichment. | RNA and protein observations differ here: bone marrow is tissue-enhanced by RNA, while hematopoietic cells are Low by IHC (HPA tissue IHC). | Use a named High IHC population to assess assay performance, then report bone-marrow staining at its observed cellular intensity (HPA tissue IHC: High placental endothelial cells; Low bone-marrow hematopoietic cells). |
Experiment evidence
IHC & IF images showing IRF1 staining
A00580-1 · IHCIHC analysis of IRF1 using anti-IRF1 antibody (A00580-1). IRF1 was detected in paraffin-embedded section of human Lung cancer tissue. Heat m
A00580-1 · IHCIHC analysis of IRF1 using anti-IRF1 antibody (A00580-1). IRF1 was detected in paraffin-embedded section of mouse intestine tissue. Heat med
A00580-1 · IFIF analysis of IRF1 using anti-IRF1 antibody (A00580-1). IRF1 was detected in immunocytochemical section of A431 cells. Enzyme antigen retri
M00580 · IHCImmunohistochemical analysis of paraffin-embedded rat kidney, using IRF1 Antibody.
M00580 · IFImmunofluorescent analysis of Hela cells, using IRF1 Antibody .
HPA · Cerebral cortexHuman Protein Atlas IHC, Cerebral cortex. Source: https://www.proteinatlas.org/ENSG00000125347-IRF1/tissue/cerebral+cortex#imid_3056912
HPA · ColonHuman Protein Atlas IHC, Colon. Source: https://www.proteinatlas.org/ENSG00000125347-IRF1/tissue/colon#imid_3051878
HPA · LiverHuman Protein Atlas IHC, Liver. Source: https://www.proteinatlas.org/ENSG00000125347-IRF1/tissue/liver#imid_3051863
HPA · GallbladderHuman Protein Atlas IHC, Gallbladder. Source: https://www.proteinatlas.org/ENSG00000125347-IRF1/tissue/gallbladder#imid_3051855
HPA · ICC-IF A-431Human Protein Atlas immunofluorescence, A-431, antibody CAB011662; green = IRF1, blue = nucleus, red = microtubules.
HPA · ICC-IF A-431Human Protein Atlas immunofluorescence, A-431, antibody CAB011662; green = IRF1, blue = nucleus, red = microtubules.
← swipe / scroll for more images →
Real IHC / IF data behind the staining-pattern expectations in this section.
Sample controls for IRF1 IHC & IF
🧪Run placenta first: endothelial cells should stain strongly (HPA: High in placenta endothelial cells). Run cerebellum as a negative comparator, focusing on granular layer cells (HPA: Not detected in cerebellum granular layer cells). On the placenta slide, compare endothelial nuclei with neighboring non-endothelial cells; cells that are negative should lack specific nuclear staining, but the supplied HPA row does not establish that every neighboring cell is negative (HPA: High in placenta endothelial cells).
Positive control tissue: Placenta (Endothelial cells, HPA High)
Negative control tissue: Cerebellum (HPA Not detected)
ICC-IF cell lines (HPA subcellular resource): HPA ICC-IF images show IRF1 in A-431, U-251MG, HaCaT, RT-4, U2OS, with annotated localisation: Nucleoplasm (approved) (HPA subcellular).
Technical controls: Include a no-primary (secondary-only) control, a concentration-matched nonimmune rabbit IgG isotype control, and an IRF1-knockout sample or validated peptide-block control (caption: rabbit anti-IRF1 antibody; standard IHC practice). Quench endogenous peroxidase and assess endogenous biotin background in placenta before interpreting signal from the biotin-based detection system (caption: biotinylated secondary and streptavidin–biotin detection; standard IHC practice).
⚠️Feasibility: A target-specific fixation window or fixation effect is unreported, and the selected A00580-1 tissue-IHC caption does not state the fixative (caption: fixative not stated). The reported paraffin-section staining used heat-mediated EDTA retrieval at pH 8.0; this supports a starting condition but does not establish retrieval dependence (caption: EDTA retrieval at pH 8.0). Frozen sections and IF cannot be ranked as easier from the supplied evidence; for placenta IHC, check vascular background from endogenous peroxidase and biotin when using the reported detection system (caption: biotinylated secondary and streptavidin–biotin detection; standard IHC practice).
HPA tissue IHC evidence for IRF1
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 | Endothelial cells | High | Protein (IHC) | HPA → |
| Testis | Pachytene spermatocytes | 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 → |
Undetected expression · recommended negative controls
| Tissue | Cell type | Level | Evidence | Source |
|---|---|---|---|---|
| Cerebellum | Cells in granular layer | Not detected | Protein (IHC) | HPA → |
| Liver | Cholangiocytes | Not detected | Protein (IHC) | HPA → |
| Lymph node | Germinal center cells | Not detected | Protein (IHC) | HPA → |
| Ovary | Ovarian stroma cells | Not detected | Protein (IHC) | HPA → |
| Prostate | Glandular cells | Not detected | Protein (IHC) | HPA → |
Section 3
Advanced IRF1 IHC Tips
Troubleshoot IRF1 staining by checking retrieval, compartment, cell identity and controls before interpreting chromogenic signal in paraffin sections.
What should I change if IRF1 staining is weak after retrieval?
Start with heat-mediated antigen retrieval in EDTA at pH 8.0 for paraffin sections (datasheet A00580-1). The selected tissue image used 1 μg/ml primary antibody overnight at 4°C, so check those conditions before changing retrieval (datasheet A00580-1). Compare weak areas with intact tissue on the same slide and a positive-control section; uneven nuclear signal can reflect uneven heating or tissue loss (standard IHC practice; HPA: nuclear and nucleolar tissue staining). If staining remains weak, vary heating duration on replicate sections while holding detection conditions constant and watching for damaged morphology (standard IHC practice). Score nuclear signal in identified cells, rather than judging retrieval by total brown area (UniProt P10914 localisation; standard IHC practice).
Could fixation explain absent nuclear IRF1 staining?
The selected paraffin-section caption does not state a fixative, so target-specific IRF1 fixation sensitivity is unknown (datasheet A00580-1). Record the specimen’s fixative and fixation interval, then compare sections processed under documented conditions with the same EDTA pH 8.0 retrieval (standard IHC practice; datasheet A00580-1). Include a positive-control section in each staining run so a failed run is distinguishable from low expression in the test specimen (standard IHC practice). Inspect nuclear detail and tissue adhesion before interpreting weak staining; poor preservation can make compartment scoring unreliable (standard IHC practice). Do not infer fixation tolerance from IRF1 topology, modifications or tissue staining patterns (UniProt P10914; HPA: tissue IHC).
How should I interpret cytoplasmic staining when I expect nuclear IRF1?
Prioritise nuclear staining because IRF1 is a transcriptional regulator found in the nucleus, while cytoplasmic localisation is also reported (UniProt P10914 localisation and function). HPA describes mainly nucleoplasmic localisation with additional cytosolic signal and nuclear or nucleolar staining across several tissues (HPA: subcellular; HPA: tissue IHC). Score nuclear and cytoplasmic compartments separately within morphologically identified cells, using the same threshold across sections (standard IHC practice). Strong diffuse cytoplasmic DAB without corresponding cellular detail warrants review of background and detection controls before biological interpretation (standard IHC practice). A change in nuclear distribution may be meaningful because MYD88-associated IRF1 migrates into the nucleus more efficiently (UniProt P10914 localisation).
Could an IRF1 isoform or modified epitope cause inconsistent staining?
The supplied record lists 0 annotated isoforms and a single 1–325 chain, so an isoform-specific explanation lacks support here (UniProt P10914 isoforms and processing). IRF1 has no transmembrane segment or signal peptide; its reported nuclear and cytoplasmic locations guide compartment assessment, not epitope accessibility (UniProt P10914 topology, processing and localisation). An N6-acetyllysine at residue 78 is annotated, but the catalog antibody’s binding epitope is unspecified (UniProt P10914 modified residues; datasheet A00580-1). Compare retrieval and antibody conditions on replicate sections before attributing differences to modification-dependent recognition (standard IHC practice). If available, use an independently validated antibody with a documented, distinct epitope to investigate discordant patterns (standard IHC practice).
How can IF help assess an ambiguous chromogenic IRF1 pattern?
Use IF as a separate localisation check, since the selected catalog evidence describes chromogenic staining of paraffin sections rather than an IF protocol (datasheet A00580-1). Multiplex IRF1 with a marker identifying the expected cell population, such as a validated endothelial marker when assessing placental endothelial cells (HPA: high IRF1 in placental endothelial cells; standard IF practice). Choose a fluorophore channel with low specimen autofluorescence and include single-channel controls before interpreting overlap (standard IF practice). Permeabilise appropriately for intracellular nuclear and cytosolic epitopes; IRF1 has no transmembrane segment (UniProt P10914 topology and localisation; standard IF practice). Check nuclear alignment against a DNA counterstain and assess bleed-through before comparing IF with DAB (standard IF practice).
What causes widespread brown signal around IRF1-positive cells?
Separate specific nuclear staining from diffuse DAB deposits by reviewing a no-primary control alongside the test section (UniProt P10914 localisation; standard IHC practice). The selected workflow used 10% goat serum blocking and biotinylated secondary detection followed by a streptavidin–biotin complex and DAB (datasheet A00580-1). Check the peroxidase block and, for this biotin-based workflow, assess endogenous biotin as possible detection background (standard IHC practice; datasheet A00580-1 detection method). Inspect section edges and damaged regions before raising the staining threshold, since artefacts there can distort scoring (standard IHC practice). Optimise washing and primary antibody exposure on matched sections if the no-primary control is clean but diffuse staining persists (standard IHC practice).
How should I quantify IRF1 across differently composed tissue sections? ⚠ ANSWER MARKED FOR VERIFICATION
Choose a predefined cell population and score nuclear IRF1 separately from cytoplasmic signal, since both locations are reported (UniProt P10914 localisation; standard IHC practice). For chromogenic sections, report the percentage of positive nuclei and an H-score based on intensity categories, with thresholds fixed before comparison (standard IHC practice). Normalise positive-cell counts to the number of eligible cells in each compartment, or report positive-cell density per mm² of viable tissue (standard IHC practice). Exclude folds, necrosis and damaged edges consistently, and document how each region was selected (standard IHC practice). Record the tissue and cell type with each score because HPA reports high, medium, low and undetected staining in different populations (HPA: tissue IHC).
How do I distinguish genuine IRF1 staining from a misleading positive?
A credible positive shows cellular nuclear staining consistent with IRF1’s transcriptional role, although cytoplasmic signal can also occur (UniProt P10914 function and localisation). Check that staining belongs to the identified cell population: HPA reports high signal in placental endothelial cells and undetected signal in liver cholangiocytes (HPA: tissue IHC). Treat edge staining, necrotic deposits and signal without intact nuclear detail as suspect until matched controls and morphology support them (standard IHC practice). Use a no-primary control to investigate endogenous enzyme or detection-system signal in DAB sections (standard IHC practice). Interpret negative cells cautiously because HPA rates tissue staining as supported with only medium consistency against RNA expression (HPA: tissue IHC reliability).
Boster reagents
Best IRF1 / Interferon regulatory factor 1 IHC Antibodies
Two anti-IRF1 antibodies have IHC images from paraffin sections: human lung cancer and mouse intestine for A00580-1, and rat kidney for M00580 (catalog IHC captions). Both also have cell IF images (catalog IF captions).
Real IHC data
Anti-IRF1 Antibody ®
Cat # A00580-1
Real IHC data
Anti-IRF1 Rabbit Monoclonal Antibody
Cat # M00580
A00580-1 will render with IHC data from human lung cancer and mouse intestine paraffin sections; its IF image shows A431 cells (A00580-1 image captions). M00580 will render with IHC data from a rat kidney paraffin section; its IF image shows HeLa cells (M00580 image captions).
Which to pick: For tissue IHC, choose A00580-1 for the pictured human or mouse samples, or M00580 for the pictured rat sample (catalog IHC captions); both captions specify paraffin sections, and neither reports the fixative (catalog IHC captions). For IF/ICC, A00580-1 has an A431 cell image and a stated 2 μg/ml IF dilution, while M00580 is monoclonal and has a HeLa cell image with a stated 1:50–1:100 IF dilution (catalog IF captions; catalog dilution fields; catalog clone field). For broader listed species reactivity, M00580 covers human, mouse and rat, versus human and mouse for A00580-1 (catalog reactivity fields).
Each figure is that product's own IHC / IF validation image from its datasheet.
References
- UniProt Consortium. UniProt entry P10914 (IRF1_HUMAN, Interferon regulatory factor 1).
- Human Protein Atlas. IRF1 tissue IHC expression (reliability: Supported).
- Human Protein Atlas. IRF1 subcellular location (ICC-IF): Mainly localized to the nucleoplasm. In addition localized to the cytosol..
- Human Protein Atlas. IRF1 antibody validation summary (3 antibodies).
- Interferon regulatory factor-1 signaling regulates the switch between autophagy and apoptosis to determine breast cancer cell fate. Cancer research 2015 — PMC4359953.
- A novel role of the TNF-α/p65/IRF1 axis in aggravating rheumatoid arthritis through the induction of fibroblast-like synoviocytes pyroptosis. Frontiers in pharmacology 2026 — PMC13472745.
- IRF1 inhibits the proliferation and metastasis of colorectal cancer by suppressing the RAS-RAC1 pathway. Cancer management and research 2019 — PMC6317468.
- IRF1 suppresses gastric tumorigenesis via dual PI3K/AKT-ERK pathway modulation and functional antagonism of oncogenic MX2. Cellular oncology (Dordrecht, Netherlands) 2026 — PMC12799679.
- PubMed PMID:2726461 — UniProt-cited evidence.
- PubMed PMID:3409321 — UniProt-cited evidence.
- PubMed PMID:1382447 — UniProt-cited evidence.
Immunohistochemistry protocol sheet for IRF1 (Interferon regulatory factor 1). Expected localisation Nuclear and nucleolar tissue staining (HPA tissue IHC). Antigen retrieval: EDTA pH 8.0 HIER, heat-mediated (datasheet A00580-1). Validated IHC antibody: A00580-1 at 0.5-1μg/ml (the product's own IHC validation image is shown). Controls (HPA): positive Placenta (Endothelial cells); negative Cerebellum. IHC-P workflow on paraffin sections; fixative unspecified. Protocol steps: 1. Sample: Paraffin-embedded human Lung cancer tissue; fixative not specified (datasheet A00580-1); 2. Fixation: Image fixative and duration unreported (datasheet A00580-1); 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 retrieval: EDTA pH 8.0 (datasheet A00580-1); 20 min, 95–100 °C (standard); 6. Peroxidase block: 3% H2O2, 10 min , room temperature (standard); 7. Blocking: 10% goat serum (datasheet A00580-1); 8. Primary antibody: Rabbit anti-IRF1, 0.5-1μg/ml (datasheet A00580-1); 9. Primary incubation: Overnight at 4 °C (datasheet A00580-1). Watch for: Fixation: Keep fixation consistent across sections (standard IHC practice; not target-specific); Caveat: Antibody staining and RNA show medium consistency (HPA tissue IHC); Isoform / epitope: No annotated isoforms; one 1–325 chain (UniProt); Regulation: Staining intensity varies by tissue cell type (HPA tissue IHC). Evidence: UniProt P10914, HPA tissue IHC · Supported, HPA ICC-IF · Mainly localized to the nucleoplasm. In addition localized to the…, Datasheet A00580-1, PMC4359953, PMC13472745. QR code links to https://www.bosterbio.com/bosterbio-gene-info-cards/IRF1/immunohistochemistry-ihc-guide.