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SIGIRR / Single Ig IL-1-related receptor · IHC design guide
Design Immunohistochemistry for SIGIRR
Plan chromogenic SIGIRR IHC in paraffin sections using the catalog antibody’s IHC protocol. Compare cytoplasmic tissue staining with membrane topology, and interpret intensity cautiously because HPA reports low consistency between staining and RNA expression.
Evidence assembled Oct 2026 · For research use; verify linked source records and product datasheet before use
SIGIRR 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 | Cytoplasmic staining (HPA tissue IHC); membrane topology (UniProt) | |
| Staining pattern | Cytoplasmic staining in most tissues (HPA tissue IHC) | |
| Antigen retrieval | EDTA pH 8.0 HIER, heat-mediated (datasheet A03373-2) | |
| Positive control | Adrenal gland+4 more · see all | |
| Negative control | Caudate+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). Selected-image fixative and duration unreported (datasheet A03373-2); verify before use. | |
| Caveat | Staining has low consistency with RNA expression (HPA tissue IHC) | |
| Regulation | Mainly epithelial expression; regulation unknown (UniProt) | |
| Isoform / epitope | 2 isoforms; map epitopes to extracellular or cytoplasmic regions (UniProt) |
Section 1
Recommended SIGIRR IHC & IF Protocols
The catalog antibody’s IHC-P protocol is paired with published chromogenic SIGIRR staining methods for prostate tissue microarrays (PMC4661098) and mouse lung sections (PMC8457575).
| Sample | Paraffin-embedded human endometrial cancer tissue; fixative not specified (datasheet A03373-2) |
| Fixation | Image fixative and duration unreported (datasheet A03373-2); 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 A03373-2); 20 min, 95–100 °C (standard) |
| Peroxidase block | 3% H2O2, 10 min, room temperature (standard) |
| Blocking | 10% goat serum (datasheet A03373-2) |
| Primary antibody | Rabbit anti-SIGIRR, 2-5 μg/ml (datasheet A03373-2) |
| Primary incubation | Overnight at 4 °C (datasheet A03373-2) |
| Detection | HRP-conjugated secondary, DAB chromogen (datasheet A03373-2) |
| Counterstain | Hematoxylin, blue, dehydrate and mount (standard) |
| Expected result | SIGIRR-positive staining in glandular cells of adrenal gland (HPA tissue IHC: High). HPA tissue profile: Cytoplasmic expression in most tissues. No signal in the no-primary control. |
💡Decision noteStart with heat-mediated EDTA retrieval at pH 8.0 (datasheet A03373-2); the included articles do not specify retrieval conditions (PMC4661098; PMC8457575).
Section 2
What Is the Expected SIGIRR Staining Pattern?
In paraffin IHC, expect mainly cytoplasmic staining in cells such as bronchial respiratory epithelium and colon glands (HPA tissue IHC). SIGIRR is a membrane protein with an extracellular region at residues 1–118, a transmembrane segment at 119–139, and a cytoplasmic region at 140–410 (UniProt Q6IA17 topology). Treat the pattern as a guide: HPA rates its tissue IHC Approved but reports low consistency between staining and RNA expression (HPA tissue IHC).
| Distinct cytoplasmic staining in bronchial respiratory epithelial cells or colon glandular cells, with little surrounding background (HPA tissue IHC). | This matches the reported IHC compartment and two High cell-specific observations (HPA tissue IHC). Record intensity by cell type; the HPA rating is Approved despite low staining–RNA consistency (HPA tissue IHC). |
| A mainly nuclear pattern replaces cytoplasmic staining in a paraffin section. | Recheck specificity and detection, because the reported tissue IHC pattern is cytoplasmic (HPA tissue IHC). Nucleoli fibrillar center staining has separate ICC-IF support and does not establish a nuclear IHC pattern (HPA subcellular ICC-IF). |
| Strong staining appears in cells expected to be undetected, such as esophageal squamous epithelium (HPA tissue IHC). | Consider cross-reactivity or endogenous detection activity before calling it SIGIRR. HPA reports Not detected specifically in esophageal squamous epithelial cells; that observation does not classify every cell in the section (HPA tissue IHC). |
| Diffuse colour covers cells, stroma, and empty spaces without a clear cellular pattern. | This is background rather than the described cytoplasmic cell pattern (HPA tissue IHC). Review blocking, washing, primary dilution, and detection controls as general IHC checks; the supplied sources do not identify a SIGIRR-specific cause. |
| No signal appears in bronchial respiratory epithelium or colon glands. | Those cell types are reported High in HPA tissue IHC. First verify that the expected cells are present and the staining run worked; HPA's low staining–RNA consistency limits how confidently one absent section can be interpreted (HPA tissue IHC). |
💡Expected SIGIRR appearanceCall a positive IHC result when bronchial respiratory epithelium or colon glands show clear, predominantly cytoplasmic staining at a relatively strong level (HPA tissue IHC: High); diffuse section-wide colour or staining restricted to an unexpected cell population warrants control review.
| Compartment and topology | HPA describes cytoplasmic staining in most tissues (HPA tissue IHC), while UniProt places SIGIRR at the membrane with residues 140–410 cytoplasmic (UniProt Q6IA17 topology). Interpret visible IHC against the observed HPA pattern; topology alone does not predict how sharply a membrane rim will stain. |
| Choice of comparison cells | Bronchial respiratory epithelium, colon glands, liver hepatocytes, and testis Leydig cells are each reported High (HPA tissue IHC). These are cell-specific reference observations, so compare the named population rather than scoring an entire organ as uniformly positive. |
| Low or undetected reference cells | Thyroid glandular cells and urinary bladder urothelial cells are reported Low; esophageal squamous epithelial cells and skeletal muscle myocytes are Not detected (HPA tissue IHC). A low reference is a weak comparator, and an undetected call applies to the listed cell type. |
| IHC evidence strength | The HPA tissue profile is Approved but notes low consistency with RNA expression; HPA023188 is IHC Approved, not listed as Enhanced (HPA tissue IHC; HPA antibodies). Use staining controls and tissue morphology when judging an unexpected result rather than treating the atlas pattern as definitive. |
| Isoforms and epitope position | UniProt lists 2 isoforms and extracellular, transmembrane, and cytoplasmic regions (UniProt Q6IA17). No epitope position or isoform coverage is supplied for the antibody, so the record cannot predict which isoform or region its IHC signal represents. |
| IF/ICC: what location is reported? | HPA reports approved cytosol and nucleoli fibrillar center locations in ICC-IF, with images from A-431, U-251MG, and U2OS (HPA subcellular ICC-IF). Those observations answer the IF location question; assess paraffin IHC against the separate HPA tissue IHC pattern. |
| Situation | Likely cause | Next action |
|---|---|---|
| Known High bronchial or colon cells are blank (HPA tissue IHC). | The expected cell population may be absent from the field, or the staining run may have failed; one blank section does not identify the cause. | Confirm morphology, run a tissue positive control, and check primary antibody, detection, and counterstain steps using general IHC practice. Interpret against HPA's low staining–RNA consistency (HPA tissue IHC). |
| Signal is faint in thyroid glandular cells or bladder urothelial cells (HPA tissue IHC). | Both populations are reported Low (HPA tissue IHC), so weak signal can fit the reference observation. | Compare with a High reference cell population on a successful run (HPA tissue IHC); do not increase primary concentration solely because a Low population stains weakly. |
| Colour is widespread across tissue and noncellular spaces. | Nonspecific background or endogenous detection activity is possible under standard chromogenic IHC practice; the supplied sources do not assign a target-specific cause. | Inspect the no-primary control, blocking, washing, and detection chemistry. Adjust one general workflow variable at a time, then check whether cell-specific cytoplasmic contrast returns (HPA tissue IHC pattern). |
| Esophageal squamous epithelium stains strongly (HPA tissue IHC). | HPA lists that specific population as Not detected (HPA tissue IHC); cross-reactivity or endogenous detection activity is possible, but staining alone cannot distinguish them. | Compare a no-primary control with the primary-stained section and review cellular localisation. Report the unexpected cell-specific finding rather than assigning it to SIGIRR without support. |
| Only nuclei stain in paraffin IHC, with no convincing cytoplasmic signal. | The pattern differs from HPA's cytoplasmic tissue IHC profile (HPA tissue IHC). HPA's nucleoli fibrillar center result comes from ICC-IF (HPA subcellular ICC-IF). | Check negative controls and the expected positive cell population, then reassess compartment scoring. Keep the ICC-IF observation distinct from the paraffin IHC interpretation. |
| Two sections give different apparent positive-cell fractions. | The sampled cell populations may differ; HPA reports staining by named cell type and notes low consistency with RNA expression (HPA tissue IHC). | Score the same morphological cell population in each section, record intensity and proportion separately, and include the HPA evidence limitation when interpreting a discrepancy (HPA tissue IHC). |
Experiment evidence
IHC & IF images showing SIGIRR staining
A03373-2 · IHCIHC analysis of SIGIRR using anti-SIGIRR antibody (A03373-2). SIGIRR was detected in a paraffin-embedded section of human endometrial cancer
A03373-2 · IHCIHC analysis of SIGIRR using anti-SIGIRR antibody (A03373-2). SIGIRR was detected in a paraffin-embedded section of human liver cancer tissu
A03373-2 · IFIF analysis of SIGIRR using anti-SIGIRR antibody (A03373-2). SIGIRR was detected in an immunocytochemical section of A549 cells. Enzyme anti
A03373 · IFImmunocytochemistry of SIGIRR in A549 cells with SIGIRR antibody at 10 μg/mL.
HPA · Cerebral cortexHuman Protein Atlas IHC, Cerebral cortex. Source: https://www.proteinatlas.org/ENSG00000185187-SIGIRR/tissue/cerebral+cortex#imid_5953288
HPA · ColonHuman Protein Atlas IHC, Colon. Source: https://www.proteinatlas.org/ENSG00000185187-SIGIRR/tissue/colon#imid_5953214
HPA · LiverHuman Protein Atlas IHC, Liver. Source: https://www.proteinatlas.org/ENSG00000185187-SIGIRR/tissue/liver#imid_5953215
HPA · KidneyHuman Protein Atlas IHC, Kidney. Source: https://www.proteinatlas.org/ENSG00000185187-SIGIRR/tissue/kidney#imid_5953208
HPA · ICC-IF A-431Human Protein Atlas immunofluorescence, A-431, antibody HPA023188; green = SIGIRR, blue = nucleus, red = microtubules.
HPA · ICC-IF A-431Human Protein Atlas immunofluorescence, A-431, antibody HPA023188; green = SIGIRR, blue = nucleus, red = microtubules.
← swipe / scroll for more images →
Real IHC / IF data behind the staining-pattern expectations in this section.
Sample controls for SIGIRR IHC & IF
🧪Run colon first: glandular cells should stain (HPA: High in colon glandular cells). Use esophageal squamous epithelium as the negative tissue (HPA: Not detected); on the colon slide, compare glandular staining with adjacent nonglandular cells, treating them as background comparators rather than confirmed negative cells.
Positive control tissue: Adrenal gland (Glandular cells, HPA High)
Negative control tissue: Caudate (HPA Not detected)
ICC-IF cell lines (HPA subcellular resource): HPA ICC-IF images show SIGIRR in A-431, U-251MG, U2OS, with annotated localisation: Nucleoli fibrillar center (approved), Cytosol (approved) (HPA subcellular).
Technical controls: Include a no-primary, secondary-only control; a concentration-matched rabbit IgG isotype control (selected-SKU caption: rabbit primary); and SIGIRR knockout tissue as a biological negative where available (standard IHC practice). In colon, assess mucus and inflammatory cells for background staining, and block endogenous peroxidase before HRP/DAB detection (standard IHC practice; selected-SKU caption: HRP/DAB).
⚠️Feasibility: Heat retrieval in EDTA at pH 8.0 is a reported starting condition for paraffin sections (selected-SKU tissue-IHC caption); whether SIGIRR staining depends on retrieval is unreported. A target-specific fixation window or fixation effect is unreported, and the exact selected-SKU caption does not state a fixative (selected-SKU tissue-IHC caption). Whether frozen sections or IF/ICC are easier is unreported; interpret IF localisation cautiously because the reported nucleolar and cytosolic signal differs from the membrane localisation annotation (HPA subcellular; UniProt Q6IA17).
HPA tissue IHC evidence for SIGIRR
Comprehensive Human Protein Atlas IHC scoring per tissue (reliability: Approved — Low 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 |
|---|---|---|---|---|
| Adrenal gland | Glandular cells | High | Protein (IHC) | HPA → |
| Bronchus | Respiratory epithelial cells | High | Protein (IHC) | HPA → |
| Colon | Glandular cells | High | Protein (IHC) | HPA → |
| Gallbladder | Glandular cells | High | Protein (IHC) | HPA → |
| Liver | Hepatocytes | High | Protein (IHC) | HPA → |
Undetected expression · recommended negative controls
| Tissue | Cell type | Level | Evidence | Source |
|---|---|---|---|---|
| Caudate | Glial cells | Not detected | Protein (IHC) | HPA → |
| Cerebellum | Cells in granular layer | Not detected | Protein (IHC) | HPA → |
| Esophagus | Squamous epithelial cells | Not detected | Protein (IHC) | HPA → |
| Oral mucosa | Squamous epithelial cells | Not detected | Protein (IHC) | HPA → |
| Ovary | Ovarian stroma cells | Not detected | Protein (IHC) | HPA → |
Section 3
Advanced SIGIRR IHC Tips
Troubleshoot SIGIRR staining in paraffin sections by checking retrieval, compartment, controls and cell-level scoring before interpreting chromogenic signal.
Which retrieval condition should I try first for weak SIGIRR staining?
Start with heat-mediated retrieval in EDTA at pH 8.0 for paraffin sections (datasheet A03373-2). The selected image pairs that retrieval with 2 μg/ml primary antibody overnight at 4°C, providing a documented starting combination (caption A03373-2). If staining remains weak, vary heating and cooling consistently across comparison sections, then consider another buffer only as a documented fallback (standard IHC practice). Compare glandular cells in colon with squamous epithelial cells in esophagus as contrasting controls, while recognising that tissue expression is context dependent (HPA: High in colon glandular cells; HPA: Not detected in esophageal squamous epithelial cells).
Could fixation explain variable SIGIRR staining between paraffin blocks?
Target-specific fixation sensitivity is unknown: the selected paraffin-section caption does not state a fixative, so it cannot establish how SIGIRR responds to fixation (caption A03373-2: fixative not stated). Record each block’s fixative, fixation duration and processing history before comparing signal, and use similarly handled sections for an optimisation series (standard IHC practice). Keep retrieval at EDTA pH 8.0 and the primary at 2 μg/ml while testing processing differences (caption A03373-2). Assess preserved morphology alongside staining; weak signal in a poorly preserved section cannot, by itself, establish low SIGIRR expression (standard IHC practice).
How should I assess membrane and cytoplasmic SIGIRR staining?
Evaluate membrane-associated staining against SIGIRR’s single transmembrane segment at residues 119–139, with an extracellular region at 1–118 and cytoplasmic region at 140–410 (UniProt Q6IA17 topology). Also record cytoplasmic signal: the tissue IHC profile describes cytoplasmic expression in most tissues (HPA: tissue profile). Do not treat a missing sharp membrane rim as proof of absence; document whether signal is membranous, cytoplasmic or diffuse in each cell population (UniProt Q6IA17 topology; HPA: tissue profile). Nucleolar fibrillar-center and cytosolic locations come from subcellular ICC/IF observations and need separate validation before being assigned to a chromogenic tissue pattern (HPA: subcellular).
How can epitope position affect SIGIRR staining in sections?
First obtain the catalog antibody’s immunogen or epitope information before attributing a staining pattern to a particular SIGIRR region; that mapping is absent from the supplied caption (caption A03373-2). SIGIRR has 2 reported isoforms, but the supplied record does not identify which residues distinguish them, so staining cannot be assigned to one isoform from these data (UniProt Q6IA17 isoforms). The extracellular region spans residues 1–118 and includes four listed glycosylation sites, whereas the cytoplasmic TIR domain spans 163–307 (UniProt Q6IA17 topology, glycosylation and domains). If an epitope becomes known, interpret retrieval-dependent changes in its regional context and verify specificity with appropriate controls (standard IHC practice).
How should I adapt the SIGIRR assessment to multiplex IF?
For the separate IF/ICC workflow, pair SIGIRR with an epithelial cell marker where that population is expected, then inspect colocalisation at the single-cell level (UniProt Q6IA17 tissue specificity; standard IF practice). Choose a fluorophore channel after checking tissue autofluorescence with an unstained section, and include single-label controls when multiplexing (standard IF practice). Permeabilisation depends on the antibody epitope: an extracellular epitope lies within residues 1–118, while a cytoplasmic epitope lies within 140–410; the supplied caption does not map this antibody’s epitope (UniProt Q6IA17 topology; caption A03373-2). Compare any cytosolic or nucleolar signal cautiously with the reported ICC/IF locations (HPA: subcellular).
What should I check when SIGIRR DAB staining is widespread?
Begin with a no-primary control to reveal signal from the detection system, and compare it with the full stain on an adjacent section (standard IHC practice). Block endogenous peroxidase before chromogenic development because the selected workflow uses a peroxidase-conjugated secondary antibody and DAB (caption A03373-2; standard IHC practice). The selected section received 10% goat serum blocking, 2 μg/ml primary overnight at 4°C, and secondary incubation for 30 minutes at 37°C (caption A03373-2). If background persists, optimise antibody concentration and washing while checking whether apparent diffuse signal follows tissue edges or damaged areas (standard IHC practice).
How should I quantify SIGIRR staining across tissue compartments? ⚠ ANSWER MARKED FOR VERIFICATION
Define the cell population and compartment before scoring, since glandular and other cells can contribute different signals within one section (HPA: tissue profile; standard IHC practice). For DAB, report the percentage of positive cells and an intensity-based H-score from 0–300, or count positive cells per mm² when cell density is the endpoint (standard IHC practice). Normalise cell counts to the measured viable tissue area, and calculate percentages and H-scores against all eligible cells of the same annotated population (standard IHC practice). Apply one threshold and imaging setup across the cohort, excluding necrotic or technically damaged regions before comparison (standard IHC practice).
How can I distinguish convincing SIGIRR signal from staining artefact?
A convincing pattern should be reproducible in intact cells and interpreted against SIGIRR’s membrane topology and reported cytoplasmic tissue staining (UniProt Q6IA17 topology; HPA: tissue profile). Check cell identity: colon glandular cells are reported High, while esophageal squamous epithelial cells are reported Not detected, though these patterns are contextual controls rather than absolute rules (HPA: tissue expression). Treat edge-restricted deposits, necrotic regions and signal retained in a no-primary control as possible artefacts, including endogenous enzyme signal in a DAB assay (standard IHC practice). Finally, avoid equating staining intensity with pathway inhibition: SIGIRR is a negative regulator of Toll-like and IL-1R signaling, but chromogenic staining alone does not measure that activity (UniProt Q6IA17 function; standard IHC interpretation).
Boster reagents
Best SIGIRR / Single Ig IL-1-related receptor IHC Antibodies
Anti-SIGIRR antibodies have IHC images from human paraffin sections and mouse kidney paraffin sections, plus IF/ICC images from human samples (catalog: A03373-2 image captions; A03373 ICC image caption).
Real IHC data
Anti-SIGIRR Antibody ®
Cat # A03373-2
Real IF data
Anti-SIGIRR Antibody
Cat # A03373
A03373-2 is listed for IHC and IF in human, mouse and rat; its IHC images show human endometrial cancer, human liver cancer, human liver and mouse kidney paraffin sections (catalog: applications, reactivity and IHC image captions). A03373 is listed for ICC in human and mouse, with an ICC image from A549 cells (catalog: applications, reactivity and ICC image caption).
Which to pick: Choose A03373-2 for tissue IHC: its own IHC captions document paraffin sections with EDTA retrieval and 2 μg/ml primary antibody; the fixative is unreported (catalog: A03373-2 IHC image captions). For IF/ICC, A03373-2 lists both applications and has corresponding images, while A03373 lists ICC and has an A549 ICC image (catalog: application lists and image captions). For work spanning human, mouse and rat, A03373-2 lists all three as reactive, though its IHC images document human and mouse samples only (catalog: A03373-2 reactivity and IHC image captions).
Each figure is that product's own IHC / IF validation image from its datasheet.
References
- UniProt Consortium. UniProt entry Q6IA17 (SIGIR_HUMAN, Single Ig IL-1-related receptor).
- Human Protein Atlas. SIGIRR tissue IHC expression (reliability: Approved).
- Human Protein Atlas. SIGIRR subcellular location (ICC-IF): Localized to the nucleoli fibrillar center and cytosol..
- Human Protein Atlas. SIGIRR antibody validation summary (1 antibodies).
- SIGIRR/TIR8, an important regulator of TLR4 and IL-1R-mediated NF-κB activation, predicts biochemical recurrence after prostatectomy in low-grade prostate carcinomas. Human pathology 2015 — PMC4661098.
- PRMT5 highly expressed on CD16 + CD56- natural killer cells is correlated with NK cells exhaustion in colorectal cancer mesenchyme. Cancer immunology, immunotherapy : CII 2025 — PMC11890482.
- Cytokine antibody array-based analysis of IL-37 treatment effects in asthma. Aging 2021 — PMC8457575.
- Loss of single immunoglobulin interlukin-1 receptor-related molecule leads to enhanced colonic polyposis in Apc(min) mice. Gastroenterology 2010 — PMC3261756.
- PubMed PMID:12975309 — UniProt-cited evidence.
- PubMed PMID:14702039 — UniProt-cited evidence.
- PubMed PMID:16554811 — UniProt-cited evidence.
Immunohistochemistry protocol sheet for SIGIRR (Single Ig IL-1-related receptor). Expected localisation Cytoplasmic staining (HPA tissue IHC); membrane topology (UniProt). Antigen retrieval: EDTA pH 8.0 HIER, heat-mediated (datasheet A03373-2). Validated IHC antibody: A03373-2 at 2-5 μg/ml (the product's own IHC validation image is shown). Controls (HPA): positive Adrenal gland (Glandular cells); negative Caudate. IHC-P workflow on paraffin sections; fixative unspecified. Protocol steps: 1. Sample: Paraffin-embedded human endometrial cancer tissue; fixative not specified (datasheet A03373-2); 2. Fixation: Image fixative and duration unreported (datasheet A03373-2); 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 A03373-2); 20 min, 95–100 °C (standard); 6. Peroxidase block: 3% H2O2, 10 min , room temperature (standard); 7. Blocking: 10% goat serum (datasheet A03373-2); 8. Primary antibody: Rabbit anti-SIGIRR, 2-5 μg/ml (datasheet A03373-2); 9. Primary incubation: Overnight at 4 °C (datasheet A03373-2). Watch for: Fixation: Keep fixation consistent across sections (standard IHC practice; not target-specific). Selected-image fixative and duration unreported (datasheet A03373-2); verify before use.; Caveat: Staining has low consistency with RNA expression (HPA tissue IHC); Isoform / epitope: 2 isoforms; map epitopes to extracellular or cytoplasmic regions (UniProt); Regulation: Mainly epithelial expression; regulation unknown (UniProt). Evidence: UniProt Q6IA17, HPA tissue IHC · Approved, HPA ICC-IF · nucleoli fibrillar center and cytosol., Datasheet A03373-2, PMC4661098, PMC8457575. QR code links to https://www.bosterbio.com/bosterbio-gene-info-cards/SIGIRR/immunohistochemistry-ihc-guide.