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STX18 / Syntaxin-18 · IHC design guide
Design Immunohistochemistry for STX18
Plan chromogenic STX18 IHC in paraffin sections around the reported cytoplasmic tissue staining (HPA tissue IHC). The catalog antibody has an IHC dilution range of 2–5 μg/ml (datasheet A11895); interpret staining with care because antibody staining and RNA expression have low consistency (HPA tissue IHC).
Evidence assembled Oct 2026 · For research use; verify linked source records and product datasheet before use
STX18 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 | General cytoplasmic staining (HPA tissue IHC); ER/Golgi membrane location (UniProt) | |
| Staining pattern | Colon glandular cells: high cytoplasmic staining (HPA tissue IHC) | |
| Antigen retrieval | EDTA pH 8.0 HIER, heat-mediated (datasheet A11895) | |
| Positive control | Colon+4 more · see all | |
| Negative control | Soft tissue+2 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 A11895); verify before use. | |
| Caveat | Staining has low consistency with RNA expression (HPA tissue IHC) | |
| Regulation | Expression regulation not specified (UniProt) | |
| Isoform / epitope | No isoforms; cytoplasmic vs luminal epitope matters (UniProt) |
Section 1
Recommended STX18 IHC & IF Protocols
Compare the catalog antibody’s IHC-P protocol (datasheet: A11895) with a published STX18 protocol using human prostate tissue microarrays (PMC4749310: Methods).
| Sample | Paraffin-embedded human appendix adenocarcinoma tissue; fixative not specified (datasheet A11895) |
| Fixation | Image fixative and duration unreported (datasheet A11895); 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 A11895); 20 min, 95–100 °C (standard) |
| Peroxidase block | 3% H2O2, 10 min, room temperature (standard) |
| Blocking | 10% goat serum (datasheet A11895) |
| Primary antibody | Rabbit anti-STX18, 2-5 μg/ml (datasheet A11895) |
| Primary incubation | Overnight at 4 °C (datasheet A11895) |
| Detection | HRP-conjugated secondary, DAB chromogen (datasheet A11895) |
| Counterstain | Hematoxylin, blue, dehydrate and mount (standard) |
| Expected result | STX18-positive staining in glandular cells of colon (HPA tissue IHC: High). HPA tissue profile: General cytoplasmic expression. No signal in the no-primary control. |
💡Decision noteStart with EDTA pH 8.0 HIER for the catalog antibody (datasheet: A11895). The published protocol does not specify retrieval conditions (PMC4749310: Methods).
Section 2
What Is the Expected STX18 Staining Pattern?
STX18 is an ER and Golgi membrane protein with a cytoplasmic region spanning residues 1–309 (UniProt Q9P2W9 topology). In paraffin IHC, expect mainly cytoplasmic staining, especially in the epithelial and glandular cell groups reported as high by HPA (HPA tissue IHC). Interpret intensity cautiously: HPA rates the tissue IHC profile Approved but reports low consistency between antibody staining and RNA expression, pending external verification (HPA tissue IHC).
| Glandular cells stain in colon, duodenum, endometrium, gallbladder, rectum or small intestine. | These cell groups are reported as High, and a cytoplasmic pattern fits the tissue profile (HPA tissue IHC). An ER-associated distribution is biologically plausible because STX18 resides on the ER membrane (UniProt Q9P2W9 subcellular location). Judge the relevant cells within the section; a dark field alone does not establish the expected pattern (general IHC practice). |
| Predominantly nuclear staining, or staining confined to an unexpected compartment, dominates the slide. | That pattern conflicts with HPA’s general cytoplasmic tissue profile and UniProt’s ER/Golgi membrane locations (HPA tissue IHC; UniProt Q9P2W9 subcellular location). Treat it as a possible staining artefact and review controls and morphology before assigning STX18 expression (general IHC practice). A membrane component can occur in IF/ICC, so compartment calls should remain application specific (HPA subcellular ICC-IF). |
| A cell group reported as Not detected stains strongly, while expected glandular cells do not. | HPA reports no detection in peripheral nerve in soft tissue, splenic red-pulp cells and vaginal squamous epithelial cells (HPA tissue IHC). Such discordance raises concern for cross-reactivity or endogenous detection activity (general IHC practice). These are comparison groups, not absolute biological negatives: the HPA tissue profile has low staining–RNA consistency and awaits external verification (HPA tissue IHC). |
| Color spreads across extracellular spaces or obscures cell borders throughout the section. | Diffuse background prevents a reliable cytoplasmic call, even where HPA reports High glandular-cell staining (HPA tissue IHC; general IHC practice). Check the detection-only control, blocking, washes and chromogen development before scoring; none of those workflow checks demonstrates a target-specific STX18 effect (general IHC practice). |
| No signal appears in a section selected for HPA High glandular-cell staining. | First confirm that the reported cell group is present and preserved; examples include colon and duodenal glandular cells (HPA tissue IHC; general IHC practice). A negative result may reflect the assay or the specimen and cannot by itself revise the HPA profile. Its Approved rating still carries a low-consistency, pending-verification caveat (HPA tissue IHC). |
💡Expected STX18 appearanceA convincing positive is discernible cytoplasmic staining in the appropriate glandular cells, with potentially High staining in HPA-listed tissues; predominantly nuclear or diffuse extracellular color is suspect (HPA tissue IHC; UniProt Q9P2W9 subcellular location; general IHC practice).
| Cell type and reference intensity | HPA reports High staining in several glandular-cell groups, respiratory epithelial cells of nasopharynx, and cells in testicular seminiferous ducts (HPA tissue IHC). It reports Low staining in ovarian stromal cells, smooth muscle cells and adipocytes (HPA tissue IHC). Compare like cell groups when judging a section; the reported levels are observations, not universal thresholds (general IHC practice). |
| Membrane topology and processing | STX18 has one transmembrane segment at residues 310–330, a cytoplasmic region at 1–309, and no listed signal peptide or propeptide (UniProt Q9P2W9 topology/processing). The record lists no isoforms, glycosylation sites or modified residues (UniProt Q9P2W9). These annotations guide compartment interpretation; they do not identify the antibody epitope or establish antigen-retrieval conditions. |
| Evidence and antibody validation | The listed HPA antibody, HPA003019, has Approved IHC status; the tissue profile has low consistency with RNA expression and is pending external verification (HPA antibodies; HPA tissue IHC). Avoid treating a single intense field or a reported Not detected group as definitive proof of specificity or absence (general IHC practice). |
| IF/ICC Q: What localization should appear? | A: HPA supports ER and plasma-membrane localization in ICC-IF and lists images from A-431, U-251MG and U2OS; UniProt also places STX18 at ER and Golgi membranes (HPA subcellular ICC-IF; UniProt Q9P2W9 subcellular location). This localization answer does not specify an IF/ICC protocol. The paraffin IHC tissue description remains general cytoplasmic expression (HPA tissue IHC). |
| Situation | Likely cause | Next action |
|---|---|---|
| A selected HPA High tissue gives no interpretable signal. | The reported positive cell group may be absent, or an assay step may have failed (HPA tissue IHC; general IHC practice). | Check morphology and a suitable positive control, then review the catalog antibody’s IHC-P procedure, detection reagents and development (general IHC practice). Do not infer STX18-specific fixation sensitivity; none is reported here. |
| The whole section has weak, widespread color. | Background from nonspecific binding, incomplete washing or detection chemistry may obscure cells (general IHC practice). | Inspect a detection-only control; review blocking, washes and development, then score only clearly cellular staining (general IHC practice). |
| Nuclei are the strongest stained compartment. | A dominant nuclear pattern disagrees with the cytoplasmic tissue profile and ER/Golgi membrane annotation (HPA tissue IHC; UniProt Q9P2W9 subcellular location). | Check counterstain and detection-only controls, then repeat interpretation against cell morphology and a reported High cell group (general IHC practice; HPA tissue IHC). |
| Splenic red-pulp or vaginal squamous cells stain strongly. | These cell groups are reported Not detected, so cross-reactivity or endogenous detection activity is possible (HPA tissue IHC; general IHC practice). | Check controls for endogenous activity and compare staining with an appropriate HPA High cell group; retain the HPA low-consistency caveat (general IHC practice; HPA tissue IHC). |
| Only tissue edges or damaged areas show intense color. | Edge concentration or damaged morphology can make local color unreliable for cell-level scoring (general IHC practice). | Assess intact interior cells and review section handling and detection controls before calling the expected cytoplasmic pattern (general IHC practice; HPA tissue IHC). |
| Staining is present, but its intensity differs from the HPA example. | HPA’s High and Low labels describe observed cell groups, while its tissue profile has low staining–RNA consistency (HPA tissue IHC). | Compare the same cell type and compartment, document controls and score the specimen on its own merits; avoid treating HPA intensity as a fixed cutoff (general IHC practice; HPA tissue IHC). |
Experiment evidence
IHC & IF images showing STX18 staining
A11895 · IHCIHC analysis of Syntaxin 18/STX18 using anti-Syntaxin 18/STX18 antibody (A11895). Syntaxin 18/STX18 was detected in a paraffin-embedded sect
A11895 · IHCIHC analysis of Syntaxin 18/STX18 using anti-Syntaxin 18/STX18 antibody (A11895). Syntaxin 18/STX18 was detected in a paraffin-embedded sect
A11895 · IFIF analysis of Syntaxin 18/STX18 using anti-Syntaxin 18/STX18 antibody (A11895). Syntaxin 18/STX18 was detected in a paraffin-embedded secti
HPA · Cerebral cortexHuman Protein Atlas IHC, Cerebral cortex. Source: https://www.proteinatlas.org/ENSG00000168818-STX18/tissue/cerebral+cortex#imid_2788944
HPA · ColonHuman Protein Atlas IHC, Colon. Source: https://www.proteinatlas.org/ENSG00000168818-STX18/tissue/colon#imid_2768082
HPA · LiverHuman Protein Atlas IHC, Liver. Source: https://www.proteinatlas.org/ENSG00000168818-STX18/tissue/liver#imid_2768075
HPA · KidneyHuman Protein Atlas IHC, Kidney. Source: https://www.proteinatlas.org/ENSG00000168818-STX18/tissue/kidney#imid_2768076
HPA · ICC-IF A-431Human Protein Atlas immunofluorescence, A-431, antibody HPA003019; green = STX18, blue = nucleus, red = microtubules.
HPA · ICC-IF A-431Human Protein Atlas immunofluorescence, A-431, antibody HPA003019; green = STX18, blue = nucleus, red = microtubules.
← swipe / scroll for more images →
Real IHC / IF data behind the staining-pattern expectations in this section.
Sample controls for STX18 IHC & IF
🧪Run colon first: its glandular cells should stain (HPA: High in colon glandular cells). Use vaginal squamous epithelium as the negative tissue (HPA: Not detected in vaginal squamous epithelial cells); on the colon slide, treat adjacent nonglandular cells as internal background only if they are intact and unstained, since no colon cell type is designated negative in the supplied HPA rows (HPA: colon glandular cells High).
Positive control tissue: Colon (Glandular cells, HPA High)
Negative control tissue: Soft tissue (HPA Not detected)
ICC-IF cell lines (HPA subcellular resource): HPA ICC-IF images show STX18 in A-431, U-251MG, U2OS, with annotated localisation: Endoplasmic reticulum (supported), Plasma membrane (supported) (HPA subcellular).
Technical controls: Include a no-primary, secondary-only control, a concentration-matched nonimmune rabbit IgG control, and tissue with confirmed STX18 knockout or a validated immunizing-peptide block (caption: rabbit primary; standard IHC practice). Block endogenous peroxidase and check whether colonic inflammatory cells or luminal material produce misleading DAB signal (standard chromogenic IHC practice).
⚠️Feasibility: A target-specific fixation window or fixation effect is unreported, and the selected A11895 paraffin-section caption does not state a fixative (caption: fixative not stated). That caption uses heat retrieval in EDTA at pH 8.0, but does not establish that retrieval is required; it also reports 2 μg/ml primary antibody overnight at 4°C (caption: IHC conditions). HPA shows ICC-IF images in A-431, U-251MG and U2OS cells, but the supplied evidence does not establish whether frozen sections or IF are easier than paraffin IHC (HPA: ICC-IF cell lines; caption: paraffin section).
HPA tissue IHC evidence for STX18
Comprehensive Human Protein Atlas IHC scoring per tissue (reliability: Approved — Low consistency between antibody staining and RNA expression data. Pending external verification.). 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 |
|---|---|---|---|---|
| Colon | Glandular cells | High | Protein (IHC) | HPA → |
| Duodenum | Glandular cells | High | Protein (IHC) | HPA → |
| Endometrium | Glandular cells | High | Protein (IHC) | HPA → |
| Gallbladder | Glandular cells | High | Protein (IHC) | HPA → |
| Nasopharynx | Respiratory epithelial cells | High | Protein (IHC) | HPA → |
Section 3
Advanced STX18 IHC Tips
Use compartment, cell type, and matched controls together when assessing STX18 staining in paraffin sections (UniProt Q9P2W9 localisation; HPA tissue IHC).
Which retrieval conditions should I try first for weak STX18 staining?
Start with heat-mediated retrieval in EDTA at pH 8.0 (datasheet A11895). The selected paraffin-section example used that retrieval before an overnight incubation at 4°C with 2 μg/ml primary antibody (datasheet A11895). If staining remains weak, compare retrieval duration on adjacent sections while keeping antibody concentration and detection conditions fixed (standard IHC practice). Assess whether the change improves glandular-cell staining in a reference section and whether background rises elsewhere; HPA reports high glandular-cell staining in colon and duodenum but cautions that antibody staining has low consistency with RNA expression (HPA tissue IHC).
Could fixation explain weak or uneven STX18 staining?
Target-specific fixation sensitivity is unknown because the selected paraffin-section caption does not state its fixative (datasheet A11895). Record the fixative, fixation duration, section age, and retrieval conditions for each block before comparing staining (standard IHC practice). Run blocks with different fixation histories through the same EDTA pH 8.0 retrieval and detection batch, then compare intact cells in equivalent regions (datasheet A11895; standard IHC practice). Uneven staining can reflect processing differences, so interpret a fixation effect only after checking section preservation and matched controls (standard IHC practice). HPA tissue patterns alone do not establish fixation sensitivity (HPA tissue IHC).
What STX18 pattern should I expect in a chromogenic section?
Expect predominantly cytoplasmic staining at light-microscope resolution: HPA describes general cytoplasmic expression, while UniProt places STX18 at endoplasmic reticulum and Golgi membranes (HPA tissue IHC; UniProt Q9P2W9 localisation). The protein has a cytoplasmic region spanning residues 1–309 and a transmembrane segment at 310–330 (UniProt Q9P2W9 topology). Compare staining within intact cells and their surrounding structures rather than treating every brown deposit as a resolved organelle (standard IHC practice). Predominantly nuclear staining would conflict with those reported locations and warrants review of the counterstain, detection controls, and antibody conditions (UniProt Q9P2W9 localisation; standard IHC practice).
How should epitope position affect my interpretation of STX18 staining?
The supplied record lists 0 isoforms and a single 1–335 chain, so it provides no isoform-specific staining prediction (UniProt Q9P2W9 processing and isoforms). Its cytoplasmic portion spans residues 1–309, followed by a membrane segment at 310–330 and a short vesicular tail at 331–335 (UniProt Q9P2W9 topology). The antibody epitope is not supplied, so do not assign weak staining to masking of a particular region (datasheet A11895). If epitope mapping becomes available, compare its location with retrieval performance on matched sections and interpret changes alongside tissue morphology (standard IHC practice).
How can I check the IHC pattern with multiplex IF?
Use IF as a separate comparison, pairing STX18 with a validated marker for the expected cell type, such as glandular cells in colon, and compare signals within the same cells (HPA tissue IHC; standard IF practice). Select a fluorophore channel with low tissue autofluorescence and include single-stain and unstained controls when assessing overlap (standard IF practice). Because residues 1–309 are cytoplasmic, a cytoplasmic epitope may require permeabilisation; the supplied evidence does not identify this antibody’s epitope (UniProt Q9P2W9 topology; datasheet A11895). Evaluate whether the IF pattern fits the reported ER and Golgi localisation without assuming that chromogenic IHC resolves those compartments (UniProt Q9P2W9 localisation; standard IHC practice).
How do I reduce diffuse brown staining without losing STX18 signal?
First compare a no-primary control with the stained section to identify signal from the detection system or tissue rather than primary-antibody binding (standard IHC practice). The selected example used 10% goat serum blocking, 2 μg/ml primary antibody overnight at 4°C, and DAB development (datasheet A11895). For excess background, review blocking, antibody concentration, washes, and DAB development on matched sections, changing one variable at a time (standard IHC practice). Include a peroxidase block as a general chromogenic workflow step and judge improvements against preserved cytoplasmic staining in an appropriate cell population (standard IHC practice; HPA tissue IHC).
How should I score STX18 IHC across tissue regions? ⚠ ANSWER MARKED FOR VERIFICATION
Define the cell population and region before scoring; HPA reports high staining in colon glandular cells and no detected staining in spleen red-pulp cells (HPA tissue IHC). For cellular staining, record an H-score or the percentage of positive cells with an intensity category, using the same thresholds across sections (standard IHC practice). If counting positive cells, express density per mm² of viable analysed tissue and document excluded edges or damaged regions (standard IHC practice). Normalise comparisons to the same eligible cell population, sampled area, staining batch, and exposure to DAB development, then report variation between regions (standard IHC practice).
How can I distinguish genuine STX18 staining from artefact?
A plausible signal occurs in the cytoplasm of intact cells, consistent with HPA tissue staining and the reported ER and Golgi membrane locations (HPA tissue IHC; UniProt Q9P2W9 localisation). Check whether glandular cells in a reference section show the expected pattern; HPA reports high staining in colon and duodenum glandular cells (HPA tissue IHC). Distrust deposits confined to section edges, necrotic areas, or the no-primary control, and check endogenous peroxidase activity when using DAB (standard IHC practice). Treat apparent nuclear-only staining cautiously, and remember that HPA rates its tissue IHC as approved while reporting low consistency with RNA expression (UniProt Q9P2W9 localisation; HPA tissue IHC).
Boster reagents
Best STX18 / Syntaxin-18 IHC Antibodies
The catalog antibody has IHC and IF images from human paraffin tissue sections (A11895 image captions; catalog reactivity).
Real IHC data
Anti-Syntaxin 18/STX18 Antibody ®
Cat # A11895
A11895 is listed for human IHC and IF (catalog applications and reactivity). Its IHC captions show appendix adenocarcinoma, breast cancer, endometrioid adenocarcinoma and penis squamous cell carcinoma; its IF captions show colon and breast cancer (A11895 image captions).
Which to pick: For tissue IHC, choose A11895 for human paraffin sections; its own IHC caption documents EDTA pH 8.0 retrieval and 2 μg/ml primary antibody (A11895 IHC caption). For IF, the same SKU has human paraffin-section images, while ICC validation is unreported (A11895 IF captions; catalog applications). No cross-species option is documented, the clone is unspecified, and the IHC caption does not report the fixative (catalog reactivity and clone; A11895 IHC caption).
Each figure is that product's own IHC / IF validation image from its datasheet.
References
- UniProt Consortium. UniProt entry Q9P2W9 (STX18_HUMAN, Syntaxin-18).
- Human Protein Atlas. STX18 tissue IHC expression (reliability: Approved).
- Human Protein Atlas. STX18 subcellular location (ICC-IF): Localized to the plasma membrane and endoplasmic reticulum..
- Human Protein Atlas. STX18 antibody validation summary (1 antibodies).
- Serum Autoantibodies in Chronic Prostate Inflammation in Prostate Cancer Patients. PloS one 2016 — PMC4749310.
- PubMed PMID:10788491 — UniProt-cited evidence.
- PubMed PMID:15489334 — UniProt-cited evidence.
- PubMed PMID:15029241 — UniProt-cited evidence.
Immunohistochemistry protocol sheet for STX18 (Syntaxin-18). Expected localisation General cytoplasmic staining (HPA tissue IHC); ER/Golgi membrane location (UniProt). Antigen retrieval: EDTA pH 8.0 HIER, heat-mediated (datasheet A11895). Validated IHC antibody: A11895 at 2-5 μg/ml (the product's own IHC validation image is shown). Controls (HPA): positive Colon (Glandular cells); negative Soft tissue. IHC-P workflow on paraffin sections; fixative unspecified. Protocol steps: 1. Sample: Paraffin-embedded human appendix adenocarcinoma tissue; fixative not specified (datasheet A11895); 2. Fixation: Image fixative and duration unreported (datasheet A11895); 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 A11895); 20 min, 95–100 °C (standard); 6. Peroxidase block: 3% H2O2, 10 min , room temperature (standard); 7. Blocking: 10% goat serum (datasheet A11895); 8. Primary antibody: Rabbit anti-STX18, 2-5 μg/ml (datasheet A11895); 9. Primary incubation: Overnight at 4 °C (datasheet A11895). Watch for: Fixation: Keep fixation consistent across sections (standard IHC practice; not target-specific). Selected-image fixative and duration unreported (datasheet A11895); verify before use.; Caveat: Staining has low consistency with RNA expression (HPA tissue IHC); Isoform / epitope: No isoforms; cytoplasmic vs luminal epitope matters (UniProt); Regulation: Expression regulation not specified (UniProt). Evidence: UniProt Q9P2W9, HPA tissue IHC · Approved, HPA ICC-IF · plasma membrane and endoplasmic reticulum., Datasheet A11895, PMC4749310. QR code links to https://www.bosterbio.com/bosterbio-gene-info-cards/STX18/immunohistochemistry-ihc-guide.