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CST1 / Cystatin-SN · IHC design guide
Design Immunohistochemistry for CST1
Plan chromogenic CST1 IHC with salivary gland as a positive tissue and adipose tissue as a negative comparator (HPA tissue IHC). Expect cytoplasmic staining in a subset of glandular cells (HPA tissue IHC), start the catalog antibody at 1:100–1:300 (datasheet), and account for CST1 secretion when interpreting staining (UniProt).
Evidence assembled Oct 2026 · For research use; verify linked source records and product datasheet before use
CST1 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 | Cytoplasm in a subset of salivary gland cells (HPA tissue IHC) | |
| Staining pattern | Subset of salivary glandular cells shows cytoplasmic staining (HPA tissue IHC) | |
| Antigen retrieval | Citrate pH 6.0 HIER, 95–98 °C, 20 min (rule: cytoplasmic / membrane antigen) | |
| Positive control | Salivary gland | |
| Negative control | Adipose tissue+4 more · see all |
Important caveats
Reasons your staining may differ from the expected pattern.
| Fixation | Keep paraffin-section fixation consistent (standard IHC practice; not target-specific) | |
| Caveat | Secreted protein may appear away from its source cells (HPA tissue IHC) | |
| Regulation | Expression regulation not specified (UniProt) | |
| Isoform / epitope | No annotated isoforms; signal peptide 1–20 is cleaved (UniProt) |
Section 1
Recommended CST1 IHC & IF Protocols
The catalog antibody’s IHC-P protocol is accompanied by published CST1 IHC methods from four articles (PMC5777761; PMC10704982; PMC3741298; PMC6767558).
| Sample | Paraffin-embedded human colon carcinoma tissue; fixative not specified (datasheet A30630) |
| Fixation | Image fixative and duration unreported (datasheet A30630); verify before use. |
| Sectioning | 4–5 µm sections on charged slides (standard) |
| Deparaffinisation | Xylene, graded ethanol series to water (standard) |
| Antigen retrieval | Heat-induced epitope retrieval in citrate buffer, pH 6.0, 20 min at 95–98 °C (standard rule: cytoplasmic / membrane antigen) |
| Peroxidase block | 3% H2O2, 10 min, room temperature (standard) |
| Blocking | 10% normal serum of the secondary host, 30 min, room temperature (standard) |
| Primary antibody | Rabbit anti-CST1, 1:100 - 1:300 (datasheet A30630) |
| Primary incubation | Overnight at 4 °C (standard) |
| Detection | HRP-polymer secondary, DAB chromogen 5–10 min (standard) |
| Counterstain | Hematoxylin, blue, dehydrate and mount (standard) |
| Expected result | CST1-positive staining in glandular cells of salivary gland (HPA tissue IHC: Medium). HPA tissue profile: Cytoplasmic expression in a subset of cells in salivary gland. No signal in the no-primary control. |
💡Decision noteStart with citrate pH 6.0 retrieval at 95–98 °C for 20 min (page antigen retrieval); adjust against the published tissue protocols.
Section 2
What Is the Expected CST1 Staining Pattern?
CST1 is secreted and has no transmembrane segment (UniProt P01037 topology). In tissue IHC, expect cytoplasmic staining in a subset of salivary glandular cells, with medium staining reported in the positive cells (HPA tissue IHC). HPA rates the tissue pattern Enhanced for consistency with RNA expression, while cautioning that secreted proteins can have different RNA and protein locations and that the target may involve protein from more than one gene (HPA tissue IHC).
| A subset of salivary glandular cells shows cytoplasmic chromogenic staining (HPA tissue IHC). | This matches the reported CST1 tissue pattern; medium staining is the HPA reference level (HPA tissue IHC). Score the stained cells and their location, rather than expecting every glandular cell to stain (HPA tissue IHC). |
| Strong nuclear or crisp plasma membrane staining dominates the section. | That compartment pattern does not match the reported cytoplasmic staining or secreted topology (HPA tissue IHC; UniProt P01037 topology). Treat it as possible artefact and check controls before assigning it to CST1 (standard IHC practice). |
| Cells outside the expected salivary glandular subset stain prominently. | The pattern needs specificity review: cross-reactivity or endogenous detection activity may contribute (standard IHC practice). HPA also cautions that the tissue target may involve protein from more than one gene (HPA tissue IHC). |
| Color spreads broadly across cells, stroma, or the whole section without a clear cellular pattern. | Diffuse staining is difficult to score as CST1 when the reference pattern is cytoplasmic staining in a subset of glandular cells (HPA tissue IHC). Compare a reagent omission control and the distribution of stain (standard IHC practice). |
| No glandular cell staining is visible in a salivary gland section. | This conflicts with the reported positive tissue pattern, though only a subset of cells is expected to stain (HPA tissue IHC). Check that the sampled area contains glandular cells, then review detection and staining controls (standard IHC practice). |
💡Expected CST1 appearanceCall a section positive when a subset of salivary glandular cells has discernible cytoplasmic staining, around the reported medium level (HPA tissue IHC); dominant nuclear staining or uniform section-wide color is suspect (HPA tissue IHC; standard IHC practice).
| Secretion and topology (UniProt P01037) | CST1 is secreted, with no transmembrane segment (UniProt P01037 topology). Interpret a cellular signal against the reported cytoplasmic glandular pattern; do not require membrane outlining (HPA tissue IHC; UniProt P01037 topology). |
| Protein processing (UniProt P01037) | The precursor has a signal peptide at residues 1–20, and the annotated chain spans residues 21–141 (UniProt P01037 processing). The payload gives no antibody epitope, so it cannot predict which form an antibody detects. |
| Tissue and fluid distribution (UniProt P01037; HPA tissue IHC) | UniProt reports protein in submandibular and sublingual saliva, but not parotid saliva; it also reports saliva, tears, urine, and seminal fluid (UniProt P01037 tissue specificity). HPA's tissue IHC reference is salivary glandular cells (HPA tissue IHC). |
| IHC evidence and specificity (HPA tissue IHC; HPA antibodies) | HPA rates the tissue profile Enhanced and lists IHC status as Supported for HPA043706 and HPA044763, and Enhanced for CAB026769 (HPA tissue IHC; HPA antibodies). Its multi-gene target caution still matters when interpreting unexpected staining (HPA tissue IHC). |
| IF/ICC: what localization can be expected? (HPA subcellular) | HPA calls CST1 secreted but provides no main subcellular location or ICC-IF cell images (HPA subcellular). Use the tissue IHC cytoplasmic pattern as context, not as an established IF/ICC staining pattern (HPA tissue IHC; HPA subcellular). |
| Situation | Likely cause | Next action |
|---|---|---|
| Salivary gland appears entirely negative. | The sampled area may miss the reported positive subset, or the staining run may have failed (HPA tissue IHC; standard IHC practice). | Inspect glandular areas and a positive control; review antibody dilution, retrieval, and detection against the run's validated procedure (standard IHC practice). No CST1-specific retrieval condition is supplied. |
| An HPA-listed negative tissue shows prominent color. | HPA reports no detection in adipocytes of adipose tissue and glandular cells of adrenal gland (HPA tissue IHC). Unexpected color may reflect nonspecific staining or endogenous activity (standard IHC practice). | Compare tissue morphology and a reagent omission control; review blocking and detection controls before calling the color CST1 (standard IHC practice). |
| The whole slide has diffuse background. | Diffuse color lacks the reported subset-of-glandular-cells pattern (HPA tissue IHC); nonspecific reagent binding or detection background are possible (standard IHC practice). | Check a reagent omission control, blocking, washing, and detection development under the validated workflow (standard IHC practice). |
| Only nuclei or cell borders show strong staining. | This differs from HPA's cytoplasmic glandular pattern and UniProt's secreted, non-transmembrane annotation (HPA tissue IHC; UniProt P01037 topology). | Recheck morphology and controls, then compare with the expected cytoplasmic pattern before scoring the section (HPA tissue IHC; standard IHC practice). |
| Staining appears in many cell types across a section. | Broad cellular staining exceeds HPA's reported salivary glandular subset and warrants specificity review (HPA tissue IHC). Endogenous activity or cross-reactivity may contribute (standard IHC practice). | Compare the pattern with an omission control and a documented positive section; assess cell identity before assigning positivity (standard IHC practice). |
| An IF/ICC image is being used to confirm the IHC pattern. | HPA supplies no ICC-IF images or main subcellular location for CST1 (HPA subcellular). | Judge the paraffin IHC section against HPA's tissue pattern and IHC antibody validation; treat the IF/ICC image as separate evidence (HPA tissue IHC; HPA antibodies; HPA subcellular). |
Experiment evidence
IHC & IF images showing CST1 staining
A30630 · IHCImmunohistochemistry analysis of paraffin-embedded human colon carcinoma tissue, using CST1 Antibody. The picture on the right is blocked wi
A30630 · IFImmunofluorescence analysis of MCF7 cells, using CST1 Antibody. The picture on the right is blocked with the synthesized peptide.
HPA · Cerebral cortexHuman Protein Atlas IHC, Cerebral cortex. Source: https://www.proteinatlas.org/ENSG00000170373-CST1/tissue/cerebral+cortex#imid_7193008
HPA · Salivary glandHuman Protein Atlas IHC, Salivary gland. Source: https://www.proteinatlas.org/ENSG00000170373-CST1/tissue/salivary+gland#imid_12572521
HPA · ColonHuman Protein Atlas IHC, Colon. Source: https://www.proteinatlas.org/ENSG00000170373-CST1/tissue/colon#imid_13117553
HPA · LiverHuman Protein Atlas IHC, Liver. Source: https://www.proteinatlas.org/ENSG00000170373-CST1/tissue/liver#imid_13117562
← swipe / scroll for more images →
Real IHC / IF data behind the staining-pattern expectations in this section.
Sample controls for CST1 IHC & IF
🧪Run salivary gland first; its glandular cells should stain (HPA: Medium). Use adrenal gland as the negative tissue (HPA: glandular cells Not detected). Nonglandular cells on the salivary slide can serve as an internal background check, but HPA does not establish them as CST1-negative (HPA: salivary gland glandular cells Medium).
Positive control tissue: Salivary gland (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 CST1; derive a cell-line control from the positive tissue's cell type (Glandular cells) and confirm it by RNA or western blot first.
Technical controls: Include a no-primary, secondary-only control and an isotype control matched to the primary antibody’s host species and monoclonal or polyclonal format (standard IHC practice). Use peptide competition as a biological specificity control (A30630 tissue-IHC caption: peptide block), and quench endogenous peroxidase for chromogenic detection (standard IHC practice).
⚠️Feasibility: A target-specific fixation window and retrieval dependence are unreported, and the A30630 paraffin-section caption does not state a fixative (A30630 tissue-IHC caption). The supplied evidence does not establish whether frozen sections or IF/ICC are easier than paraffin IHC (A30630 tissue-IHC caption; HPA: no ICC-IF cell-line images). Because CST1 is secreted, distinguish staining of glandular cells from signal in luminal secretions (UniProt P01037: secreted; HPA: salivary gland glandular cells Medium).
HPA tissue IHC evidence for CST1
Comprehensive Human Protein Atlas IHC scoring per tissue (reliability: Enhanced — High consistency between antibody staining and RNA expression data. Caution, targets protein from more than one gene. 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 |
|---|---|---|---|---|
| Salivary gland | 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 CST1 IHC Tips
Use cell distribution and secretion biology to evaluate CST1 staining in paraffin sections, with antibody specificity and tissue processing assessed separately.
How should I optimize retrieval when CST1 staining is weak?
Start with citrate buffer at pH 6.0 for heat-induced retrieval at 95–98 °C for 20 min (page retrieval rule). Run a known positive salivary gland section alongside the specimen, since glandular cells show medium staining in the tissue reference (HPA tissue IHC). If staining remains weak, compare a shorter heating interval or an alternative retrieval buffer on serial sections while keeping antibody incubation and detection constant (standard IHC practice). Score signal and tissue damage together: stronger diffuse color without preserved glandular morphology does not establish improved CST1 detection, especially for a secreted protein (UniProt P01037; standard IHC practice).
Does fixation explain absent CST1 staining in my paraffin sections?
Target-specific sensitivity to fixation is unknown from the supplied evidence, so an absent result cannot be assigned to fixation alone (provided evidence). The A30630 tissue image uses paraffin-embedded colon carcinoma, but its caption does not state the fixative or fixation duration (A30630 caption). For a controlled comparison, process adjacent samples with documented fixation times, apply the same pH 6.0 retrieval, and include a positive glandular-cell control on each run (page retrieval rule; HPA tissue IHC; standard IHC practice). Compare preserved morphology and staining together, and record the processing history before interpreting differences as biological expression (standard IHC practice).
Where should CST1 staining appear, and when is extracellular signal credible?
Expect cytoplasmic staining in a subset of salivary gland cells, rather than uniform staining of every glandular cell (HPA tissue IHC). CST1 has a 1–20 signal peptide, a 21–141 mature chain, and no transmembrane segment; secretion can therefore separate the producing cell from detected protein (UniProt P01037). Examine glandular cells and nearby luminal material separately, recording whether staining follows intact structures or pools at damaged edges (UniProt P01037; standard IHC practice). Treat extracellular color as provisional until it reproduces in well-preserved sections and exceeds the matched negative-control signal (standard IHC practice).
How can I assess whether the antibody distinguishes CST1 from related cystatins?
The record lists 0 isoforms and a mature 21–141 chain, but it does not locate the antibody epitope (UniProt P01037; provided evidence). Related salivary cysteine proteinase inhibitors can be immunologically related while differing in sequence, so morphology alone cannot prove CST1-specific recognition (UniProt P01037). The A30630 colon carcinoma image includes a synthesized-peptide blocking comparison; loss of staining supports recognition of that competing peptide, but does not establish exclusivity against related proteins (A30630 caption; standard IHC interpretation). Check the catalog antibody's stated immunogen sequence against related cystatins, then prioritize an independent antibody or orthogonal expression assay when specificity determines the conclusion (standard IHC practice).
How should I evaluate CST1 in a multiplex fluorescence experiment?
Use this as an exploratory IF comparison: the supplied antibody image documents paraffin-section IHC, while no CST1 ICC/IF images are listed in the subcellular reference (A30630 caption; HPA subcellular). Pair CST1 with a validated glandular-cell marker, since the tissue reference reports cytoplasmic staining in a subset of salivary gland cells (HPA tissue IHC; standard IF practice). Select a far-red fluorophore when tissue autofluorescence is prominent, and acquire unstained and single-color controls before interpreting overlap (standard IF practice). Because the epitope is unspecified and CST1 lacks a transmembrane segment, compare gentle permeabilisation for intracellular signal with an unpermeabilised section for accessible extracellular signal; do not assume both preparations measure the same pool (provided evidence; UniProt P01037; standard IF practice).
What should I change when brown staining obscures glandular cells?
First compare the stained section with a no-primary control and the peptide-blocked comparison, assessing whether color remains in the same structures (A30630 caption; standard IHC practice). Quench endogenous peroxidase before chromogenic detection and inspect any residual brown deposits in the control; these are workflow checks, not evidence of CST1 expression (standard IHC practice). Titrate the primary antibody and shorten chromogen development one variable at a time, retaining the pH 6.0 retrieval condition during that comparison (page retrieval rule; standard IHC practice). Give greatest weight to reproducible glandular-cell staining with preserved morphology, the distribution reported by the tissue reference (HPA tissue IHC; standard IHC practice).
How should I score heterogeneous CST1 staining across sections? ⚠ ANSWER MARKED FOR VERIFICATION
Define the region of interest before scoring and exclude folds, tears, necrosis, and section edges by the same rule in every sample (standard IHC practice). For intact glandular cells, report the percentage positive and an H-score using intensity categories 0–3; retain the raw counts behind each score (standard IHC practice). If extracellular deposits are the outcome, measure stained area or signal density per mm² of viable tissue separately from cellular scores (UniProt P01037; standard IHC practice). Normalize cellular counts to evaluable glandular cells and area measurements to viable tissue area, then compare runs against the same positive control because CST1 is secreted and tissue location may differ from RNA location (UniProt P01037; HPA tissue IHC; standard IHC practice).
What would make a CST1-positive IHC result convincing?
A convincing result reproduces in intact glandular cells with the cytoplasmic pattern reported in salivary gland, while accounting separately for plausible secreted material (HPA tissue IHC; UniProt P01037). Require signal above no-primary background and examine whether peptide competition reduces the catalog antibody's staining in a matched comparison (A30630 caption; standard IHC practice). Treat edge staining, necrotic deposits, and residual endogenous-peroxidase color as artefact candidates until their distribution is resolved with controls and tissue morphology (standard IHC practice). Interpret unexpected cells cautiously: the tissue reference warns that its antibody can recognize protein from more than one gene, and secretion can separate protein staining from the site of RNA expression (HPA tissue IHC).
Boster reagents
Best CST1 / Cystatin-SN IHC Antibodies
Anti-CST1 antibody A30630 has real IHC data from paraffin-embedded human colon carcinoma tissue and IF data from MCF7 cells (catalog IHC/IF captions); listed reactivity covers human, mouse and rat (catalog reactivity).
Real IHC data
Anti-CST1/Cystatin Sn Antibody
Cat # A30630
A30630 will render with an IHC image of paraffin-embedded human colon carcinoma tissue and a peptide-blocked comparison (catalog IHC image caption). Its IF image shows MCF7 cells and a peptide-blocked comparison; IHC, IF and ICC are listed applications (catalog IF image caption; catalog applications).
Which to pick: For tissue IHC, choose A30630: it is a rabbit polyclonal antibody with a listed IHC dilution of 1:100–1:300 and an image from paraffin-embedded human colon carcinoma tissue (catalog host/clonality/dilution; catalog IHC image caption). For IF/ICC, the same SKU lists both applications and a dilution of 1:200–1:1000, with IF shown in MCF7 cells (catalog applications/dilution; catalog IF image caption). For mouse or rat samples, A30630 lists reactivity to both species; the supplied IHC caption identifies human tissue, and its fixative is unreported (catalog reactivity; catalog IHC image caption).
Each figure is that product's own IHC / IF validation image from its datasheet.
References
- UniProt Consortium. UniProt entry P01037 (CYTN_HUMAN, Cystatin-SN).
- Human Protein Atlas. CST1 tissue IHC expression (reliability: Enhanced).
- Human Protein Atlas. CST1 subcellular location (ICC-IF): Secreted.
- Human Protein Atlas. CST1 antibody validation summary (3 antibodies).
- Prognostic significance of cystatin SN associated nomograms in patients with colorectal cancer. Oncotarget 2017 — PMC5777761.
- Combination of serum CST1 and HE4 for early diagnosis of endometrial cancer. PeerJ 2023 — PMC10704982.
- Cystatin SN upregulation in patients with seasonal allergic rhinitis. PloS one 2013 — PMC3741298.
- Upregulation of cystatin SN promotes hepatocellular carcinoma progression and predicts a poor prognosis. Journal of cellular physiology 2019 — PMC6767558.
- PubMed PMID:3446578 — UniProt-cited evidence.
- PubMed PMID:2837486 — UniProt-cited evidence.
- PubMed PMID:11780052 — UniProt-cited evidence.
Immunohistochemistry protocol sheet for CST1 (Cystatin-SN). Expected localisation Cytoplasm in a subset of salivary gland cells (HPA tissue IHC). Antigen retrieval: Citrate pH 6.0 HIER, 95–98 °C, 20 min (rule: cytoplasmic / membrane antigen). Validated IHC antibody: A30630 at 1:100 - 1:300 (the product's own IHC validation image is shown). Controls (HPA): positive Salivary gland (Glandular cells); negative Adipose tissue. IHC-P workflow on paraffin sections; fixative unspecified. Protocol steps: 1. Sample: Paraffin-embedded human colon carcinoma tissue; fixative not specified (datasheet A30630); 2. Fixation: Image fixative and duration unreported (datasheet A30630); 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-induced epitope retrieval in citrate buffer, pH 6.0 , 20 min at 95–98 °C…; 6. Peroxidase block: 3% H2O2, 10 min , room temperature (standard); 7. Blocking: 10% normal serum of the secondary host, 30 min , room temperature (standard); 8. Primary antibody: Rabbit anti-CST1, 1:100 - 1:300 (datasheet A30630); 9. Primary incubation: Overnight at 4 °C (standard). Watch for: Fixation: Keep paraffin-section fixation consistent (standard IHC practice; not target-specific); Caveat: Secreted protein may appear away from its source cells (HPA tissue IHC); Isoform / epitope: No annotated isoforms; signal peptide 1–20 is cleaved (UniProt); Regulation: Expression regulation not specified (UniProt). Evidence: UniProt P01037, HPA tissue IHC · Enhanced, HPA ICC-IF · Secreted, Datasheet A30630, PMC5777761, PMC10704982. QR code links to https://www.bosterbio.com/bosterbio-gene-info-cards/CST1/immunohistochemistry-ihc-guide.