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CTRC / Chymotrypsin-C · IHC design guide
Design Immunohistochemistry for CTRC
Plan chromogenic IHC for CTRC in paraffin sections using pancreatic exocrine staining as the reference pattern (HPA tissue IHC). The catalog antibody’s human pancreas example uses 2 μg/ml primary antibody and DAB detection (datasheet A03540-1).
Evidence assembled Oct 2026 · For research use; verify linked source records and product datasheet before use
CTRC 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 and extracellular in pancreas (HPA tissue IHC) | |
| Staining pattern | Exocrine cells show cytoplasmic and extracellular staining (HPA tissue IHC) | |
| Antigen retrieval | EDTA pH 8.0 HIER, heat-mediated (datasheet A03540-1) | |
| Positive control | Pancreas | |
| Negative control | Adipose tissue+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 | Secretion may extend staining beyond producing cells (HPA tissue IHC) | |
| Regulation | Pancreas enriched; regulation unreported (UniProt) | |
| Isoform / epitope | No isoforms; processing may affect cellular and secreted epitopes (UniProt; HPA tissue IHC) |
Section 1
Recommended CTRC IHC & IF Protocols
The catalog antibody’s IHC-P protocol (datasheet A03540-1) and a published protocol for CTRC staining in tumor and peritumoral tissues (PMC6154863) provide starting conditions.
| Sample | Paraffin-embedded rat pancreas tissue; fixative not specified (datasheet A03540-1) |
| Fixation | Image fixative and duration unreported (datasheet A03540-1); 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 A03540-1); 20 min, 95–100 °C (standard) |
| Peroxidase block | 3% H2O2, 10 min, room temperature (standard) |
| Blocking | 10% goat serum (datasheet A03540-1) |
| Primary antibody | Rabbit anti-CTRC, 2-5 μg/ml (datasheet A03540-1) |
| Primary incubation | Overnight at 4 °C (datasheet A03540-1) |
| Detection | HRP-conjugated secondary, DAB chromogen (datasheet A03540-1) |
| Counterstain | Hematoxylin, blue, dehydrate and mount (standard) |
| Expected result | CTRC-positive staining in exocrine glandular cells of pancreas (HPA tissue IHC: Medium). HPA tissue profile: Distinct cytoplasmic expression as well as extracellular positivity in pancreas. No signal in the no-primary control. |
💡Decision noteStart with heat-mediated EDTA retrieval at pH 8.0 (datasheet A03540-1). The published tissue protocol used citrate at pH 6.0 for 15 minutes (PMC6154863).
Section 2
What Is the Expected CTRC Staining Pattern?
CTRC should show distinct cytoplasmic staining in pancreatic exocrine glandular cells, with extracellular positivity also expected (HPA: pancreas IHC, Enhanced reliability). Its signal peptide and lack of a transmembrane segment are consistent with secretion (UniProt Q99895: signal 1–16; topology). HPA reports that the tissue locations of RNA and secreted protein may differ (HPA: tissue IHC reliability description).
| Distinct cytoplasmic staining in pancreatic exocrine glandular cells, with adjacent extracellular positivity. | This matches the reported tissue pattern. The exocrine glandular cell staining level is Medium; extracellular signal can accompany a secreted protein (HPA: pancreas IHC; HPA: Secreted). |
| Predominantly nuclear staining or a crisp cell-surface outline, without the expected cytoplasmic pattern. | Treat this as a localisation mismatch requiring review, rather than a confirmed CTRC pattern. HPA reports cytoplasmic and extracellular positivity; UniProt lists no transmembrane segment and does not assign a subcellular location (HPA: pancreas IHC; UniProt Q99895: topology, subcellular annotation). |
| Strong staining in an unexpected cell population while pancreatic exocrine glandular cells are weak or negative. | Consider cross-reactivity or detection background. Cell identity matters: HPA reports CTRC staining in pancreatic exocrine glandular cells, while its listed adipocytes, respiratory epithelial cells and glial cells are Not detected in their respective tissues (HPA: tissue IHC). |
| A uniform haze covers cells and extracellular spaces, including a control section processed without primary antibody. | A signal that persists without primary antibody suggests background from the detection workflow, such as endogenous enzyme activity in chromogenic IHC. This is a general IHC interpretation, not an HPA finding about CTRC; it obscures the distinct pancreatic pattern reported by HPA (HPA: pancreas IHC). |
| No convincing signal in pancreatic exocrine glandular cells on an otherwise readable section. | This conflicts with the reported positive reference tissue. First check that exocrine glandular cells are present and assess the assay controls; absent signal alone cannot distinguish technical failure from a difference between samples or antibodies (HPA: pancreas IHC, Medium, Enhanced reliability; general IHC practice). |
💡Expected CTRC appearanceCall a section positive when pancreatic exocrine glandular cells show distinct medium cytoplasmic staining, possibly with extracellular positivity; isolated nuclear or crisp membrane staining is a pattern mismatch (HPA: pancreas IHC; UniProt Q99895: topology).
| Tissue and cell context | Use pancreatic exocrine glandular cells as the positive reference: HPA reports Medium staining there and Not detected staining in its listed negative cell populations. Those findings describe the sampled tissues, not every cell type or specimen (HPA: tissue IHC). |
| Secretion and precursor processing | CTRC has a signal peptide at residues 1–16, a propeptide at 17–29, and a listed chain at 30–268 (UniProt Q99895: processing). Its reported extracellular positivity is consistent with secretion (HPA: pancreas IHC; HPA: Secreted). An antibody epitope in a removed segment could affect what it detects; no epitope is supplied here, so this remains conditional. |
| Antibody evidence | HPA lists antibody HPA046920 as rabbit polyclonal with Enhanced IHC validation; its tissue reliability description reports high agreement between staining and RNA data (HPA: antibody record; HPA: tissue IHC). This supports the reported pattern but supplies no dilution, retrieval condition or epitope for another antibody. |
| IF/ICC Q&A: Is the IHC pattern an IF/ICC localisation reference? | Use it as a tissue level expectation only. HPA calls CTRC Secreted, but lists no main ICC-IF location or cell line images, and the listed antibody has no ICC validation status (HPA: subcellular record; HPA: antibody record). An IF/ICC result therefore needs its own controls and interpretation. |
| Situation | Likely cause | Next action |
|---|---|---|
| Pancreatic exocrine glandular cells show no staining. | The assay may have failed, the relevant cells may be absent, or this specimen may differ from HPA's reference; the slide alone cannot distinguish these possibilities (HPA: pancreas IHC; general IHC practice). | Confirm exocrine glandular cells on the counterstain, review positive and negative assay controls, and check the antibody's documented IHC-P conditions before changing one workflow variable at a time (general IHC practice). |
| The whole section develops brown signal, including a no-primary control. | The pattern suggests detection-system background or endogenous chromogenic activity, not a cell-specific CTRC call (general IHC practice). | Review the no-primary control, blocking and endogenous enzyme suppression appropriate to the detection system; rescore only after the background clears (general IHC practice). |
| Staining is mainly nuclear or outlines cell membranes. | This differs from HPA's cytoplasmic and extracellular pancreatic pattern; UniProt reports no transmembrane segment, but gives no subcellular annotation (HPA: pancreas IHC; UniProt Q99895: topology, subcellular annotation). | Check morphology and compartment assignment, then compare with the pancreatic positive reference and detection controls before accepting the signal as CTRC (HPA: pancreas IHC; general IHC practice). |
| Unexpected cells stain strongly while the expected exocrine cells do not. | Cross-reactivity or local background is plausible; HPA's positive call is for pancreatic exocrine glandular cells, and its listed negative populations are Not detected (HPA: tissue IHC). | Identify the stained cells on the counterstain and compare a reported negative tissue under the same run conditions; treat discordant staining as unconfirmed (HPA: tissue IHC; general IHC practice). |
| Extracellular signal is present but cytoplasmic exocrine staining is hard to see. | Extracellular positivity is part of the reported pattern for this secreted protein; it does not by itself establish which nearby cells produced the signal (HPA: pancreas IHC; HPA: Secreted). | Inspect intact exocrine glandular cells at suitable magnification and score cellular and extracellular staining separately, using the HPA pattern as the reference (HPA: pancreas IHC; general IHC practice). |
| An IF/ICC image is being judged against the IHC section. | HPA provides no main ICC-IF location or cell line images, and its listed antibody has no ICC validation status (HPA: subcellular record; HPA: antibody record). | Interpret the IF/ICC result with its own controls and avoid assigning a precise intracellular location from the tissue IHC pattern alone (HPA: pancreas IHC; HPA: subcellular record; general IF practice). |
Experiment evidence
IHC & IF images showing CTRC staining
A03540-1 · IHCIHC analysis of CTRC using anti-CTRC antibody (A03540-1). CTRC was detected in a paraffin-embedded section of rat pancreas tissue. Heat medi
A03540-1 · IHCIHC analysis of CTRC using anti-CTRC antibody (A03540-1). CTRC was detected in a paraffin-embedded section of human pancreas tissue. Heat me
HPA · Cerebral cortexHuman Protein Atlas IHC, Cerebral cortex. Source: https://www.proteinatlas.org/ENSG00000162438-CTRC/tissue/cerebral+cortex#imid_13276363
HPA · ColonHuman Protein Atlas IHC, Colon. Source: https://www.proteinatlas.org/ENSG00000162438-CTRC/tissue/colon#imid_13265425
HPA · LiverHuman Protein Atlas IHC, Liver. Source: https://www.proteinatlas.org/ENSG00000162438-CTRC/tissue/liver#imid_13265418
HPA · PancreasHuman Protein Atlas IHC, Pancreas. Source: https://www.proteinatlas.org/ENSG00000162438-CTRC/tissue/pancreas#imid_13265377
← swipe / scroll for more images →
Real IHC / IF data behind the staining-pattern expectations in this section.
Sample controls for CTRC IHC & IF
🧪Run pancreas first: exocrine glandular cells should stain (HPA: Medium in pancreas exocrine glandular cells). Use adipose tissue adipocytes as the negative tissue (HPA: Not detected in adipocytes); on the pancreas slide, use non-exocrine stromal cells as background comparators that should show only counterstain or background, while recognizing that their CTRC status is not established by the supplied HPA row (HPA: exocrine glandular cells are the reported positive cell type).
Positive control tissue: Pancreas (Exocrine glandular cells, HPA Medium)
Negative control tissue: Adipose tissue (HPA Not detected)
ICC-IF cell lines (HPA subcellular resource): HPA carries no ICC-IF cell line for CTRC; derive a cell-line control from the positive tissue's cell type (Exocrine glandular cells) and confirm it by RNA or western blot first.
Technical controls: Run a no-primary, secondary-only control and a matched nonimmune rabbit IgG isotype control, and confirm specificity with CTRC-knockout tissue if available (caption: rabbit primary and goat anti-rabbit secondary). Block endogenous peroxidase in pancreas before chromogenic detection (caption: pancreas stained with HRP/DAB).
⚠️Feasibility: A target-specific fixation window or fixation effect is unreported, and the selected A03540-1 paraffin-section caption does not state a fixative (caption: rat pancreas paraffin section; fixative not stated). Paraffin IHC is demonstrated with heat retrieval in EDTA at pH 8.0, but whether retrieval is required is unreported (caption: EDTA retrieval). The supplied evidence does not establish that frozen sections or IF/ICC are easier (HPA: no ICC-IF image cell lines); handle pancreas promptly to limit autolysis, a practical concern for protease-rich pancreatic tissue (UniProt Q99895: protease).
HPA tissue IHC evidence for CTRC
Comprehensive Human Protein Atlas IHC scoring per tissue (reliability: Enhanced — High consistency between antibody staining and RNA expression data. Secreted protein, tissue location of RNA and protein is expected to differ.). 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 |
|---|---|---|---|---|
| Pancreas | Exocrine glandular cells | Medium | Protein (IHC) | HPA → |
Undetected expression · recommended negative controls
| Tissue | Cell type | Level | Evidence | Source |
|---|---|---|---|---|
| Adipose tissue | Adipocytes | Not detected | Protein (IHC) | HPA → |
| Adrenal gland | Glandular cells | Not detected | Protein (IHC) | HPA → |
| Appendix | Glandular cells | Not detected | Protein (IHC) | HPA → |
| Bone marrow | Hematopoietic cells | Not detected | Protein (IHC) | HPA → |
| Breast | Adipocytes | Not detected | Protein (IHC) | HPA → |
Section 3
Advanced CTRC IHC Tips
Troubleshoot CTRC staining in paraffin sections by checking retrieval, tissue pattern, and controls against the reported pancreas IHC evidence (datasheet A03540-1; HPA tissue IHC).
Which retrieval conditions should I start with for CTRC IHC?
Start with heat-mediated antigen retrieval in EDTA at pH 8.0 for paraffin sections (datasheet A03540-1). The reported rat pancreas staining used this retrieval before blocking with 10% goat serum and incubating the antibody at 2 μg/ml overnight at 4°C (datasheet A03540-1). If staining is weak, adjust heating duration in small steps while keeping the same buffer, and compare section integrity and background on matched sections (standard IHC practice). Include a pancreas positive control in each run because exocrine glandular cells show medium staining and extracellular positivity has also been reported there (HPA tissue IHC).
How should I troubleshoot weak CTRC staining after fixation?
The selected antibody caption identifies a paraffin-embedded rat pancreas section but does not state its fixative, so target-specific fixation sensitivity is unknown (datasheet A03540-1). Record the fixative and fixation duration for each specimen, then compare matched sections processed with the same retrieval and detection conditions (standard IHC practice). Use the reported EDTA pH 8.0 heat retrieval as the starting condition, and assess tissue morphology alongside signal when changing processing conditions (datasheet A03540-1; standard IHC practice). A pancreas control can show whether a run stained as expected, but cannot establish that an individual specimen retained its CTRC epitope (HPA tissue IHC; standard IHC practice).
Where should credible CTRC staining appear in pancreas sections?
Expect staining in pancreatic exocrine glandular cells, with distinct cytoplasmic expression and extracellular positivity reported in pancreas (HPA tissue IHC). CTRC has a signal peptide at residues 1–16 and no annotated transmembrane segment, while HPA describes the protein as secreted (UniProt Q99895 processing and topology; HPA subcellular). Score cellular and extracellular staining separately so deposited extracellular signal does not inflate the proportion of positive cells (HPA tissue IHC; standard IHC practice). If staining is predominantly nuclear or concentrated in unrelated tissue compartments, compare it with a negative tissue and a no-primary control before assigning it to CTRC (HPA tissue IHC; standard IHC practice).
Could CTRC processing or epitope placement change the IHC pattern?
The record lists a signal peptide at residues 1–16, a propeptide at 17–29, and a chymotrypsin-C chain at 30–268 (UniProt Q99895 processing). It also lists glycosylation sites at residues 25, 52, and 226, but gives no antibody epitope, so the effect of these features on staining cannot be assigned (UniProt Q99895 glycosylation; datasheet A03540-1). No isoforms are listed in the supplied record; that alone does not establish antibody specificity for every processed form (UniProt Q99895 isoforms; standard IHC practice). If staining differs between specimens, compare matched processing and controls before attributing the difference to cleavage or glycosylation (standard IHC practice).
How can I adapt CTRC localisation checks to multiplex IF?
For a separate IF experiment, pair CTRC with a validated exocrine glandular cell marker, since those cells show pancreatic IHC positivity (HPA tissue IHC). Choose a fluorophore and acquisition channel with low measured autofluorescence in the specimen, and include unstained and single-label controls before interpreting overlap (standard IF practice). Permeabilise when testing the reported cytoplasmic signal, but compare a nonpermeabilised section when testing accessible extracellular signal; CTRC has no annotated transmembrane segment (HPA tissue IHC; UniProt Q99895 topology; standard IF practice). Optimise the IF antibody and fixation conditions separately because the supplied caption documents chromogenic paraffin-section IHC, not an IF validation (datasheet A03540-1).
What should I check when pancreatic CTRC IHC has diffuse background?
First compare a no-primary control with the stained section to assess secondary reagent and chromogen background (standard IHC practice). The reported protocol used 10% goat serum, a peroxidase-conjugated secondary for 30 minutes at 37°C, and DAB detection; these are documented conditions, not proof that every diffuse deposit is CTRC (datasheet A03540-1). Include a peroxidase block when using HRP and DAB, and inspect whether deposits follow tissue edges, damaged areas, or endogenous enzyme activity (standard IHC practice). Preserve plausible extracellular pancreatic signal during optimisation because extracellular positivity accompanies cytoplasmic staining in the reference pattern (HPA tissue IHC).
How should I quantify CTRC staining across pancreas sections? ⚠ ANSWER MARKED FOR VERIFICATION
Define the analysis region as viable exocrine glandular tissue and record the fraction of positive cells plus staining intensity, for example an H-score from 0–300 using intensity grades 0–3 (HPA tissue IHC; standard IHC scoring practice). Normalise the positive-cell count to all evaluable exocrine glandular cells in that region, using the same threshold across specimens (standard IHC scoring practice). Measure extracellular staining separately as positive area per mm² of evaluable tissue, since extracellular positivity is part of the reported pancreatic pattern (HPA tissue IHC; standard image analysis practice). Exclude folds, edges, and necrotic areas using prespecified rules, and inspect controls before comparing groups (standard IHC practice).
How do I distinguish true CTRC staining from artefact?
Give greatest weight to reproducible cytoplasmic staining in pancreatic exocrine glandular cells, while allowing extracellular positivity in the same tissue (HPA tissue IHC). A predominantly nuclear pattern conflicts with that reported distribution, and strong signal in negative-control tissue needs investigation before a CTRC assignment (HPA tissue IHC; standard IHC practice). Examine edges and necrotic regions for local deposits, and use a no-primary control plus peroxidase blocking to assess chromogen signal unrelated to primary antibody binding (standard IHC practice). Adipocytes in adipose tissue and glandular cells in adrenal gland are reported as not detected, making them useful pattern checks when appropriately processed (HPA tissue IHC).
Boster reagents
Best CTRC / Chymotrypsin-C IHC Antibodies
A03540-1 has real IHC images from paraffin-embedded rat and human pancreas sections (catalog IHC image captions). IF/ICC validation is not reported (catalog applications; IF image alts absent).
Real IHC data
Anti-CTRC Antibody ®
Cat # A03540-1
A03540-1 is the only SKU and lists IHC with human and rat reactivity (catalog applications/reactivity). Its captions document staining in paraffin-embedded rat and human pancreas sections; the rendered card shows the rat section (catalog IHC image captions; card figure tag).
Which to pick: Choose A03540-1 for tissue IHC: this rabbit polyclonal antibody has paraffin-section pancreas captions for rat and human, with EDTA pH 8.0 retrieval and 2 μg/ml primary antibody documented in the rat caption (catalog host/dilution_raw; IHC image captions). For cross-species IHC, the same SKU lists human and rat reactivity and has an image caption for each (catalog reactivity; IHC image captions). No IF/ICC protocol option is supported here, and the IHC captions do not report the fixative (catalog applications; IF image alts absent; IHC image captions).
Each figure is that product's own IHC / IF validation image from its datasheet.
References
- UniProt Consortium. UniProt entry Q99895 (CTRC_HUMAN, Chymotrypsin-C).
- Human Protein Atlas. CTRC tissue IHC expression (reliability: Enhanced).
- Human Protein Atlas. CTRC subcellular location (ICC-IF): Secreted.
- Human Protein Atlas. CTRC antibody validation summary (1 antibodies).
- Co-targeting ALK and EGFR parallel signaling in oral squamous cell carcinoma. Oral oncology 2016 — PMC5460536.
- Label-Free Quantitative Proteomics Unravels Carboxypeptidases as the Novel Biomarker in Pancreatic Ductal Adenocarcinoma. Translational oncology 2018 — PMC6154863.
- Tumour response to TRK inhibition in a patient with pancreatic adenocarcinoma harbouring an NTRK gene fusion. Annals of oncology : official journal of the European Society for Medical Oncology 2019 — PMC6859823.
- PubMed PMID:8635596 — UniProt-cited evidence.
- PubMed PMID:14702039 — UniProt-cited evidence.
- PubMed PMID:16710414 — UniProt-cited evidence.
Immunohistochemistry protocol sheet for CTRC (Chymotrypsin-C). Expected localisation Cytoplasmic and extracellular in pancreas (HPA tissue IHC). Antigen retrieval: EDTA pH 8.0 HIER, heat-mediated (datasheet A03540-1). Validated IHC antibody: A03540-1 at 2-5 μg/ml (the product's own IHC validation image is shown). Controls (HPA): positive Pancreas (Exocrine glandular cells); negative Adipose tissue. IHC-P workflow on paraffin sections; fixative unspecified. Protocol steps: 1. Sample: Paraffin-embedded rat pancreas tissue; fixative not specified (datasheet A03540-1); 2. Fixation: Image fixative and duration unreported (datasheet A03540-1); 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 A03540-1); 20 min, 95–100 °C (standard); 6. Peroxidase block: 3% H2O2, 10 min , room temperature (standard); 7. Blocking: 10% goat serum (datasheet A03540-1); 8. Primary antibody: Rabbit anti-CTRC, 2-5 μg/ml (datasheet A03540-1); 9. Primary incubation: Overnight at 4 °C (datasheet A03540-1). Watch for: Fixation: Keep fixation consistent across sections (standard IHC practice; not target-specific); Caveat: Secretion may extend staining beyond producing cells (HPA tissue IHC); Isoform / epitope: No isoforms; processing may affect cellular and secreted epitopes (UniProt; HPA tissue IHC); Regulation: Pancreas enriched; regulation unreported (UniProt). Evidence: UniProt Q99895, HPA tissue IHC · Enhanced, HPA ICC-IF · Secreted, Datasheet A03540-1, PMC6154863. QR code links to https://www.bosterbio.com/bosterbio-gene-info-cards/CTRC/immunohistochemistry-ihc-guide.