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PREP / Prolyl endopeptidase · IHC design guide
Design Immunohistochemistry for PREP
Plan chromogenic IHC for PREP in paraffin sections using its cytoplasmic tissue staining profile (HPA tissue IHC). The guide covers fixation, controls, antibody dilution and interpretation of staining across cell types.
Evidence assembled Oct 2026 · For research use; verify linked source records and product datasheet before use
PREP 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 tissue staining (HPA tissue IHC) | |
| Staining pattern | Cytoplasmic staining, high in glandular cells (HPA tissue IHC) | |
| Antigen retrieval | EDTA pH 8.0 HIER, heat-mediated (datasheet A00298-2) | |
| Positive control | Colon+4 more · see all | |
| Negative control | None in HPA (detected in all 45 tissues); use no-primary + isotype controls |
Important caveats
Reasons your staining may differ from the expected pattern.
| Fixation | Keep fixation conditions consistent across sections. (standard IHC practice; not target-specific) | |
| Caveat | Low adipocyte staining may mimic a weak assay (HPA tissue IHC) | |
| Regulation | No expression regulator annotated (UniProt) | |
| Isoform / epitope | No isoforms; one chain spans residues 1–710 (UniProt) |
Section 1
Recommended PREP IHC & IF Protocols
The catalog antibody uses EDTA pH 8.0 retrieval (datasheet: A00298-2). One published PREP protocol describes dewaxed brain sections and citrate retrieval (PMC4589196).
| Sample | Paraffin-embedded human breast cancer tissue; fixative not specified (datasheet A00298-2) |
| Fixation | Image fixative and duration unreported (datasheet A00298-2); 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 A00298-2); 20 min, 95–100 °C (standard) |
| Peroxidase block | 3% H2O2, 10 min, room temperature (standard) |
| Blocking | 10% goat serum (datasheet A00298-2) |
| Primary antibody | Rabbit anti-PREP, 2-5μg/ml (datasheet A00298-2) |
| Primary incubation | Overnight at 4 °C (datasheet A00298-2) |
| Detection | Streptavidin-biotin complex (SABC), DAB chromogen (datasheet A00298-2) |
| Counterstain | Hematoxylin, blue, dehydrate and mount (standard) |
| Expected result | PREP-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 for the catalog antibody (datasheet: A00298-2); compare citrate pH 6.0 if needed (PMC4589196). Verify secondary antibody compatibility with the primary.
Section 2
What Is the Expected PREP Staining Pattern?
PREP is a cytoplasmic protein with no transmembrane segment (UniProt P48147). In paraffin section IHC, expect cytoplasmic staining in glandular cells, especially in colon, duodenum, endometrium and rectum, where HPA reports high staining. HPA rates its tissue pattern Supported, with medium consistency between staining and RNA expression and external verification pending (HPA tissue IHC).
| Distinct cytoplasmic stain in glandular cells of colon, duodenum, endometrium or rectum. | This matches the reported high staining in those cells (HPA tissue IHC) and PREP's cytoplasmic location (UniProt P48147). Compare the signal with the surrounding tissue and the negative control on the same run. |
| Predominantly nuclear or sharply membrane-bound stain, with little cytoplasmic signal. | That distribution conflicts with the reported cytoplasmic pattern (UniProt P48147; HPA tissue IHC). Consider nonspecific staining, section artefact or detection artefact before assigning it to PREP. |
| Strong, uniform stain in cells expected to show low signal, such as adipocytes or smooth muscle cells. | HPA reports low staining in these cells (HPA tissue IHC). Assess cross-reactivity and, for enzyme-based chromogenic detection, endogenous activity. Low reported staining does not mean every cell must be blank. |
| Diffuse chromogen across cells and surrounding tissue, without clear cytoplasmic boundaries. | This is difficult to score as PREP: the expected pattern is cellular and cytoplasmic (HPA tissue IHC). Review negative controls, blocking, antibody concentration and chromogen development as general IHC checks. |
| No stain in glandular cells of an otherwise suitable colon or duodenum section. | Both are high-staining examples (HPA tissue IHC), so an absent signal calls for assay review. Check tissue preservation, retrieval conditions, antibody and detection controls; HPA does not establish which step failed. |
💡Expected PREP appearanceCall a section positive when glandular cells show clear, predominantly cytoplasmic staining, with strong signal in HPA high examples such as colon or duodenum (HPA tissue IHC; UniProt P48147); isolated nuclear, membrane-bound or diffuse background signal is suspect.
| Cellular location and topology | PREP is cytoplasmic and has no transmembrane segment (UniProt P48147); score the cell body rather than a membrane rim. Compartment alone cannot establish antibody specificity. |
| Tissue pattern | HPA reports high glandular-cell staining in colon, duodenum, endometrium and rectum, and low tissue specificity at the RNA level (HPA tissue IHC). Use the high examples as practical positive references. |
| Strength of tissue evidence | The tissue IHC pattern is Supported, with medium staining–RNA consistency and external verification pending (HPA tissue IHC). Treat an unexpected pattern as a finding to verify, not a definitive PREP result. |
| Antibody validation | HPA lists IHC as Supported for HPA031388, HPA031389, HPA031390 and CAB025414 (HPA antibodies). That status applies to the listed antibodies; it does not validate every catalog antibody. |
| Fixation and retrieval | Target-specific fixation sensitivity and a PREP retrieval condition are unreported in these payloads. If signal fails, review the IHC-validated antibody's stated conditions and controls as a general IHC workflow check. |
| IF/ICC Q&A: Where should PREP appear? | In cells imaged by ICC-IF, HPA supports cytosolic localization (HPA subcellular). Use the separate IF/ICC guide for that application; this section supplies no IF/ICC protocol option. |
| Situation | Likely cause | Next action |
|---|---|---|
| Positive-reference glandular cells show no stain. | An assay or specimen problem is possible; colon and duodenum glandular cells are high-staining references (HPA tissue IHC). | Confirm the positive control, then review section quality, retrieval, antibody application and detection steps. Do not infer PREP-specific fixation sensitivity from this failure. |
| Staining is mostly nuclear or outlines membranes. | The location conflicts with cytoplasmic PREP (UniProt P48147; HPA tissue IHC). The pattern may reflect nonspecific staining or artefact. | Inspect the negative control and tissue morphology; repeat with an IHC-validated antibody or an independent antibody where available. |
| Smooth muscle cells or adipocytes stain as strongly as the proposed positive cells. | HPA reports low staining in those cell types (HPA tissue IHC). Cross-reactivity or chromogenic background may be contributing. | Compare with a high-staining reference tissue and negative control; check endogenous detection activity if the chosen chromogen system is susceptible. |
| Chromogen covers much of the section with poor cell detail. | Diffuse background obscures the cellular cytoplasmic pattern reported by HPA (HPA tissue IHC); excessive reagent signal is one possible general IHC cause. | Review blocking, washing, antibody concentration and development time against the assay instructions. Score only signal that remains cell-associated. |
| Only faint cytoplasmic stain appears in a low-staining tissue. | A weak result can fit HPA's low calls for cholangiocytes, smooth muscle cells, chondrocytes or adipocytes (HPA tissue IHC). | Check the same run's high-staining reference before calling the assay unsuccessful. Record cell type and intensity rather than treating every weak cell as negative. |
| An IF/ICC image is needed to judge the compartment. | HPA supports cytosolic localization by ICC-IF (HPA subcellular), but fluorescence images answer a separate application question. | Compare location with HPA's cytosolic call and consult the separate IF/ICC guide; do not substitute its conditions for paraffin section IHC. |
Experiment evidence
IHC & IF images showing PREP staining
A00298-2 · IHCIHC analysis of Prolyl Endopeptidase/PREP using anti-Prolyl Endopeptidase/PREP antibody (A00298-2). Prolyl Endopeptidase/PREP was detected i
A00298-2 · IHCIHC analysis of Prolyl Endopeptidase/PREP using anti-Prolyl Endopeptidase/PREP antibody (A00298-2). Prolyl Endopeptidase/PREP was detected i
A00298 · IHCImmunohistochemical analysis of paraffin-embedded rat-brain, antibody was diluted at 1:100
A00298 · IHCImmunohistochemical analysis of paraffin-embedded mouse-brain, antibody was diluted at 1:100
HPA · Cerebral cortexHuman Protein Atlas IHC, Cerebral cortex. Source: https://www.proteinatlas.org/ENSG00000085377-PREP/tissue/cerebral+cortex#imid_6598872
HPA · ColonHuman Protein Atlas IHC, Colon. Source: https://www.proteinatlas.org/ENSG00000085377-PREP/tissue/colon#imid_6597230
HPA · LiverHuman Protein Atlas IHC, Liver. Source: https://www.proteinatlas.org/ENSG00000085377-PREP/tissue/liver#imid_6597215
HPA · KidneyHuman Protein Atlas IHC, Kidney. Source: https://www.proteinatlas.org/ENSG00000085377-PREP/tissue/kidney#imid_6597216
HPA · ICC-IF A-431Human Protein Atlas immunofluorescence, A-431, antibody HPA031390; green = PREP, blue = nucleus, red = microtubules.
HPA · ICC-IF A-431Human Protein Atlas immunofluorescence, A-431, antibody HPA031390; green = PREP, blue = nucleus, red = microtubules.
← swipe / scroll for more images →
Real IHC / IF data behind the staining-pattern expectations in this section.
Sample controls for PREP IHC & IF
🧪Run colon first and score its glandular cells for strong staining (HPA: High in colon glandular cells). HPA detects PREP in all 45 scored tissues, so use no-primary and isotype controls for the negative comparison; nonglandular cells on the colon slide can provide a background reference but should not be designated PREP-negative (HPA: no negative tissue rows).
Positive control tissue: Colon (Glandular cells, HPA High)
Negative control tissue: None in HPA: PREP is detected in all 45 scored tissues. Use a no-primary (secondary-only) and an isotype control instead.
ICC-IF cell lines (HPA subcellular resource): HPA ICC-IF images show PREP in A-431, U-251MG, U2OS, NIH 3T3, with annotated localisation: Cytosol (supported) (HPA subcellular).
Technical controls: Include a no-primary, secondary-only slide, an isotype control matched to the catalog primary’s host species and clonality, and a PREP knockout specimen or validated peptide-block control (selected-SKU caption: rabbit primary antibody). For colon chromogenic IHC, quench endogenous peroxidase and assess endogenous biotin background when using the caption’s biotinylated secondary and SABC detection (selected-SKU caption: biotinylated secondary, SABC and DAB).
⚠️Feasibility: A target-specific fixation window or fixation effect is unreported, and the selected-SKU paraffin-section caption does not state the fixative (selected-SKU caption: fixative not stated). The caption reports heat retrieval in EDTA at pH 8.0, but does not establish that PREP staining depends on retrieval or that frozen sections or IF are easier; ICC-IF images are available for this gene (selected-SKU caption: EDTA retrieval; HPA: ICC-IF images). In colon, assess luminal material and gland edges for background before scoring cytoplasmic staining (HPA: High in colon glandular cells; UniProt P48147: cytoplasm).
HPA tissue IHC evidence for PREP
Comprehensive Human Protein Atlas IHC scoring per tissue (reliability: Supported — Medium 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 → |
| Rectum | Glandular cells | High | Protein (IHC) | HPA → |
| Adrenal gland | Glandular cells | Medium | Protein (IHC) | HPA → |
Undetected expression · recommended negative controls
| Tissue | Cell type | Level | Evidence | Source |
|---|---|---|---|---|
| None in HPA: PREP is detected in all 45 scored tissues. Use a no-primary (secondary-only) and an isotype control instead. | ||||
Section 3
Advanced PREP IHC Tips
Troubleshoot PREP staining in paraffin sections by checking retrieval, cytoplasmic localisation, cell identity and controls before comparing chromogenic signal.
What retrieval conditions should I start with for PREP in paraffin sections?
Start with heat-mediated retrieval in EDTA at pH 8.0 for paraffin sections (datasheet A00298-2). The selected tissue image used that retrieval before incubation with 2 μg/ml primary antibody overnight at 4°C, so reproduce those conditions when comparing your staining with it (caption A00298-2). If signal is weak, verify that sections stayed immersed during heating and that retrieval and cooling were consistent across the run (standard IHC practice). Evaluate any alternative retrieval buffer only as a controlled fallback, keeping antibody concentration, detection and exposure to chromogen constant so its effect can be judged (standard IHC practice).
How should I troubleshoot weak PREP staining when fixation history is uncertain?
PREP-specific sensitivity to fixation is unknown from the supplied evidence, and the selected paraffin-section caption does not state a fixative (caption A00298-2). Record the fixative and processing history for each specimen, then compare sections processed under matched conditions before changing retrieval or antibody concentration (standard IHC practice). Use the documented EDTA pH 8.0 retrieval and 2 μg/ml primary incubation as a reproducible starting point for this antibody (caption A00298-2). Include a known staining reference section in the same run, because a difference between batches cannot establish a PREP-specific fixation effect by itself (standard IHC practice).
Where should convincing PREP staining appear in chromogenic IHC?
Score PREP primarily as cytoplasmic staining: UniProt places it in the cytoplasm, and HPA reports general cytoplasmic tissue expression (UniProt P48147; HPA tissue IHC). HPA further supports a cytosolic location in subcellular images, consistent with the absence of a transmembrane segment in the record (HPA subcellular; UniProt P48147 topology). Check whether the signal fills the cytoplasm of morphologically intact cells rather than forming only a sharp membrane rim or isolated nuclear deposit (standard IHC practice; UniProt P48147 localisation). Review a counterstained serial section and a no-primary control before attributing an unexpected compartment pattern to PREP (standard IHC practice).
Could an isoform or altered epitope explain uneven PREP staining?
The supplied UniProt record annotates 0 isoforms and a single 1–710 chain, so it offers no annotated isoform pattern to explain regional staining (UniProt P48147). PREP has no annotated transmembrane segment or glycosylation sites, while acetylation is recorded at residues 1 and 157 (UniProt P48147). The antibody epitope is not supplied, so those modifications cannot be linked to a staining change without epitope or validation data (supplied antibody evidence; UniProt P48147). If staining varies, compare intact areas under identical EDTA pH 8.0 retrieval and detection conditions before proposing an epitope-based explanation (caption A00298-2; standard IHC practice).
How can IF help assess an ambiguous PREP IHC pattern?
Use IF as a separate corroborating experiment and pair PREP with a marker for the expected glandular cell population, because HPA reports high staining in colon, duodenum, endometrium and rectum glandular cells (HPA tissue IHC). Select spectrally separated fluorophores after checking tissue autofluorescence and single-stain controls, then compare each channel with the chromogenic section (standard IF practice). PREP is cytosolic and lacks a transmembrane segment, so permeabilise cells for cytosolic antibody access while recognising that the antibody epitope is unspecified (HPA subcellular; UniProt P48147 topology; supplied antibody evidence). Keep IF fixation and antibody conditions documented separately; the supplied paraffin IHC caption provides no IF fixation or validation conditions (caption A00298-2).
What should I check when PREP DAB staining is diffuse or widespread?
Run a no-primary control and inspect whether pigment remains after the same secondary, detection and DAB steps (standard IHC practice). The selected image used 10% goat serum, biotinylated goat anti-rabbit secondary for 30 minutes at 37°C, and a streptavidin–biotin complex with DAB, which makes each step worth checking against controls (caption A00298-2). Block endogenous peroxidase and assess endogenous biotin when using this detection chemistry; these are general chromogenic IHC controls, not PREP-specific findings (standard IHC practice). Interpret broad cytoplasmic staining cautiously because HPA describes general cytoplasmic expression and low tissue RNA specificity (HPA tissue IHC).
How should I quantify PREP staining across tissue regions? ⚠ ANSWER MARKED FOR VERIFICATION
Define viable, morphologically comparable regions before scoring and record cytoplasmic signal in the intended cell population (standard IHC practice; UniProt P48147 localisation). For a per-cell readout, report percent positive cells and an H-score using intensity grades 0–3, yielding a possible range of 0–300 (standard IHC practice). If counting positive cells instead, report density per mm² of evaluated viable tissue and state whether stromal cells were included (standard IHC practice). Normalise comparisons to the same cell population, viable area, staining run and scoring threshold; HPA shows differing glandular-cell staining levels across tissues (standard IHC practice; HPA tissue IHC).
How can I distinguish true PREP staining from tissue artefact?
A plausible positive pattern is cytoplasmic staining in intact cells, with glandular cells providing a useful reference because HPA reports high levels in several glandular tissues (UniProt P48147 localisation; HPA tissue IHC). Treat isolated nuclear or membrane-only deposits, section-edge enhancement and staining confined to necrotic areas as patterns requiring control review (UniProt P48147 localisation; standard IHC practice). Compare those areas with a no-primary section to detect signal from the secondary or chromogenic detection system, including endogenous enzyme activity (standard IHC practice). HPA rates its tissue profile Supported but notes medium agreement with RNA and pending external verification, so corroborate unexpected cell-specific claims independently (HPA tissue IHC).
Boster reagents
Best PREP / Prolyl endopeptidase IHC Antibodies
Two anti-PREP antibodies have real paraffin-section IHC images: human cancer tissue for A00298-2 and rat and mouse brain for A00298 (catalog IHC captions). A00298 also lists IF (catalog applications).
Real IHC data
Anti-Prolyl Endopeptidase/PREP Antibody ®
Cat # A00298-2
Real IHC data
Anti-Prolyl endopeptidase PREP Antibody
Cat # A00298
A00298-2 has IHC images from paraffin-embedded human breast, liver, pancreatic and prostate cancer tissue and lists Human and Rat reactivity (catalog IHC captions; catalog reactivity). A00298 has paraffin-embedded rat and mouse brain IHC images and lists Human, Mouse and Rat reactivity plus IF (catalog IHC captions; catalog reactivity; catalog applications).
Which to pick: Choose A00298-2 for human tissue IHC when its documented EDTA pH 8.0 retrieval and 2 μg/ml primary incubation fit the experiment (A00298-2 IHC captions); the captions report paraffin embedding but do not report the fixative (A00298-2 IHC captions). Choose A00298 for rat or mouse brain paraffin-section IHC, or as the IF option; IF is listed at 1:50, but no IF image or ICC validation is supplied (A00298 IHC captions; catalog applications and dilution; catalog IF images). A00298 offers the broadest listed species coverage—Human, Mouse and Rat—while A00298-2 lists Human and Rat (catalog reactivity).
Each figure is that product's own IHC / IF validation image from its datasheet.
References
- UniProt Consortium. UniProt entry P48147 (PPCE_HUMAN, Prolyl endopeptidase).
- Human Protein Atlas. PREP tissue IHC expression (reliability: Supported).
- Human Protein Atlas. PREP subcellular location (ICC-IF): Localized to the cytosol..
- Human Protein Atlas. PREP antibody validation summary (4 antibodies).
- LncPrep + 96kb inhibits ovarian fibrosis by upregulating prolyl oligopeptidase expression. Molecular medicine reports 2025 — PMC11894593.
- The expression levels of prolyl oligopeptidase responds not only to neuroinflammation but also to systemic inflammation upon liver failure in rat models and cirrhotic patients. Journal of neuroinflammation 2015 — PMC4589196.
- Laser capture microdissection--a demonstration of the isolation of individual dopamine neurons and the entire ventral tegmental area. Journal of visualized experiments : JoVE 2015 — PMC4354571.
- Increased Expression of Prolyl Endopeptidase Induced by Oxidative Stress in Nucleus Pulposus Cells Aggravates Intervertebral Disc Degeneration. Oxidative medicine and cellular longevity 2022 — PMC9020979.
- PubMed PMID:7959018 — UniProt-cited evidence.
- PubMed PMID:8089089 — UniProt-cited evidence.
- PubMed PMID:14574404 — UniProt-cited evidence.
Immunohistochemistry protocol sheet for PREP (Prolyl endopeptidase). Expected localisation Cytoplasmic tissue staining (HPA tissue IHC). Antigen retrieval: EDTA pH 8.0 HIER, heat-mediated (datasheet A00298-2). Validated IHC antibody: A00298-2 at 2-5μg/ml (the product's own IHC validation image is shown). Controls (HPA): positive Colon (Glandular cells); negative None in HPA (detected in all 45 tissues); use no-primary + isotype controls. IHC-P workflow on paraffin sections; fixative unspecified. Protocol steps: 1. Sample: Paraffin-embedded human breast cancer tissue; fixative not specified (datasheet A00298-2); 2. Fixation: Image fixative and duration unreported (datasheet A00298-2); 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 A00298-2); 20 min, 95–100 °C (standard); 6. Peroxidase block: 3% H2O2, 10 min , room temperature (standard); 7. Blocking: 10% goat serum (datasheet A00298-2); 8. Primary antibody: Rabbit anti-PREP, 2-5μg/ml (datasheet A00298-2); 9. Primary incubation: Overnight at 4 °C (datasheet A00298-2). Watch for: Fixation: Keep fixation conditions consistent across sections. (standard IHC practice; not target-specific); Caveat: Low adipocyte staining may mimic a weak assay (HPA tissue IHC); Isoform / epitope: No isoforms; one chain spans residues 1–710 (UniProt); Regulation: No expression regulator annotated (UniProt). Evidence: UniProt P48147, HPA tissue IHC · Supported, HPA ICC-IF · cytosol., Datasheet A00298-2, PMC4589196. QR code links to https://www.bosterbio.com/bosterbio-gene-info-cards/PREP/immunohistochemistry-ihc-guide.