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CTSG / Cathepsin G · IHC design guide
Design Immunohistochemistry for CTSG
Use bone marrow hematopoietic cells as a strong positive reference and tonsil non-germinal center cells as a moderate reference (HPA tissue IHC). This guide covers chromogenic CTSG staining in paraffin sections and interpretation of its cytoplasmic tissue pattern (HPA tissue IHC).
Evidence assembled Oct 2026 · For research use; verify linked source records and product datasheet before use
CTSG 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 | Selective cytoplasmic staining in lymphoid and hematopoietic cells (HPA tissue IHC) | |
| Staining pattern | Cytoplasmic signal in subsets of lymphoid and hematopoietic cells (HPA tissue IHC) | |
| Antigen retrieval | EDTA pH 8.0 HIER, heat-mediated (datasheet PB10053) | |
| Positive control | Bone marrow+3 more · see all | |
| Negative control | Adipose tissue+4 more · see all |
Important caveats
Reasons your staining may differ from the expected pattern.
| Fixation | Keep fixation consistent across paraffin sections. (standard IHC practice; not target-specific) | |
| Caveat | Secretion by activated neutrophils may obscure the cell of origin (UniProt) | |
| Regulation | Neutrophil activation promotes secretion (UniProt) | |
| Isoform / epitope | No isoforms reported; cleaved propeptides may alter epitope detection (UniProt) |
Section 1
Recommended CTSG IHC & IF Protocols
Compare the catalog antibody’s IHC-P protocol (datasheet: PB10053) with three published CTSG chromogenic IHC protocols (PMC11290089; PMC10878333; PMC13563026).
| Sample | Paraffin-embedded human tonsil tissue; fixative not specified (datasheet PB10053) |
| Fixation | Image fixative and duration unreported (datasheet PB10053); 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 PB10053); 20 min, 95–100 °C (standard) |
| Peroxidase block | 3% H2O2, 10 min, room temperature (standard) |
| Blocking | 10% goat serum (datasheet PB10053) |
| Primary antibody | Rabbit anti-CTSG, 2-5μg/ml (datasheet PB10053) |
| Primary incubation | Overnight at 4 °C (datasheet PB10053) |
| Detection | HRP-conjugated secondary, DAB chromogen (datasheet PB10053) |
| Counterstain | Hematoxylin, blue, dehydrate and mount (standard) |
| Expected result | CTSG-positive staining in hematopoietic cells of bone marrow (HPA tissue IHC: High). HPA tissue profile: Selective cytoplasmic expression in subsets of lymphoid and hematopoietic cells. No signal in the no-primary control. |
💡Decision noteStart with heat-mediated EDTA pH 8.0 retrieval for the catalog antibody (datasheet: PB10053); the cited studies used different or unspecified retrieval conditions (PMC11290089; PMC10878333; PMC13563026).
Section 2
What Is the Expected CTSG Staining Pattern?
In paraffin-section IHC, expect selective cytoplasmic CTSG staining in subsets of lymphoid and hematopoietic cells, strongest in bone marrow hematopoietic cells (HPA: Enhanced tissue-IHC reliability; High in bone marrow). A granular cytoplasmic pattern is consistent with its granule and lysosome locations; CTSG has no transmembrane segment (UniProt P08311: subcellular location and topology). Interpret staining by both cell identity and compartment.
| Strong, selective cytoplasmic staining in bone marrow hematopoietic cells (HPA: High). | This is the clearest tissue positive in the supplied record. Granular cytoplasmic signal fits CTSG's granule location; assess stained cells rather than assigning positivity to the whole section (UniProt P08311: cytoplasmic granule; HPA: selective expression). |
| Moderate staining in lymph node or tonsil non-germinal center cells, or spleen red-pulp cells (HPA: Medium). | These are supported positive populations, with lower reported staining than bone marrow hematopoietic cells (HPA: tissue IHC). A negative neighboring cell does not invalidate selective staining; review the annotated cell population (HPA: selective cytoplasmic expression). |
| Predominantly nuclear staining in otherwise intact cells, without selective cytoplasmic signal (HPA: tissue IHC). | Treat this as a compartment mismatch and investigate staining artefact or antibody specificity. Nuclear CTSG is reported during apoptosis, so isolated nuclear signal needs cell-context review before rejection (UniProt P08311: nuclear localization during apoptosis). |
| Broad staining of bronchial respiratory epithelium or adrenal glandular cells (HPA: Not detected in these cells). | Confirm which cells carry the signal; adjacent hematopoietic cells may account for focal positivity (HPA: selective hematopoietic expression). Persistent staining in the annotated negative cells raises cross-reactivity or endogenous chromogen activity (general IHC practice). |
| Diffuse color across cells and tissue, or no signal in bone marrow hematopoietic cells (HPA: High). | Either result obscures the expected selective pattern. Diffuse color calls for background and detection controls; absent bone marrow signal calls for a positive-control and reagent-workflow check (HPA: tissue IHC; general IHC practice). |
💡Expected CTSG appearanceCall IHC positive when selected hematopoietic cells show High bone marrow or Medium lymphoid-tissue cytoplasmic staining; broad staining of annotated negative cells is suspect (HPA: tissue IHC), and a granular appearance fits CTSG localization (UniProt P08311: cytoplasmic granule).
| Tissue and cell selection (HPA: tissue IHC). | Bone marrow hematopoietic cells provide the strongest listed positive; lymph node and tonsil non-germinal center cells and spleen red-pulp cells are Medium. Compare the specified populations, not entire tissue fields (HPA: tissue IHC). |
| Intracellular location and secretion (UniProt P08311: subcellular location). | CTSG occurs in cytoplasmic granules and lysosomes and is secreted by activated neutrophils. Extracellular material may therefore require context; it cannot replace selective cellular staining as the tissue-IHC readout (UniProt P08311; HPA: tissue IHC). |
| Protein processing (UniProt P08311: signal peptide and mature chains). | The precursor has a signal peptide at residues 1–18 and propeptides at 19–20 and 245–255; reported mature chains span 21–244 or 21–243. Epitope-dependent differences are possible, but no antibody epitope is supplied (UniProt P08311). |
| Antibody validation (HPA: HPA047737 and CAB000110, IHC Enhanced). | Both listed antibodies carry IHC Enhanced status, and the tissue profile has Enhanced reliability from staining–RNA consistency. This supports the reported pattern but does not establish performance of an unlisted reagent (HPA: antibody validation and tissue IHC). |
| Retrieval and chromogenic detection (general IHC practice). | Optimize retrieval and detection against positive and negative controls when troubleshooting paraffin sections. The supplied sources give no CTSG-specific retrieval condition or fixation-sensitivity result; do not infer one from HPA staining levels or UniProt topology (HPA: tissue IHC; UniProt P08311: topology). |
| Situation | Likely cause | Next action |
|---|---|---|
| Bone marrow hematopoietic cells lack staining (HPA: High). | The run may have failed, or the chosen retrieval and detection conditions may be inadequate (general IHC practice). The supplied sources do not establish CTSG-specific fixation sensitivity. | Check a bone marrow positive control, antibody application, retrieval run and detection reagents; repeat with a controlled adjustment if the run failed (HPA: High in bone marrow; general IHC practice). |
| Most cells show diffuse cytoplasmic color (HPA: selective expression expected). | Background may reflect nonspecific binding, excessive antibody or detection signal, or incomplete washes (general IHC practice). | Review no-primary and negative controls; adjust blocking, antibody dilution, washes and detection exposure while preserving the bone marrow positive control (general IHC practice; HPA: High in bone marrow). |
| Annotated negative epithelial or glandular cells stain strongly (HPA: bronchus and adrenal gland, Not detected). | Misidentified infiltrating cells, cross-reactivity, or endogenous enzyme activity may explain color in the field (HPA: selective hematopoietic expression; general IHC practice). | Identify the stained cells morphologically and compare negative controls; check the chromogen and endogenous-enzyme blocking before calling those cells CTSG-positive (general IHC practice; HPA: tissue IHC). |
| Color persists in a no-primary control (general IHC practice). | A chromogenic detection component or endogenous tissue activity can create signal independent of the primary antibody (general IHC practice). | Inspect secondary and substrate controls and review endogenous-enzyme blocking; score CTSG only after antibody-independent color is resolved (general IHC practice). |
| Nuclear staining dominates while cytoplasmic staining is absent (HPA: selective cytoplasmic expression). | A staining artefact or off-target signal is possible, although CTSG can localize to nuclei during apoptosis (UniProt P08311: subcellular location). | Review cell morphology and the bone marrow positive-control pattern; avoid interpreting widespread nuclear staining as the expected tissue-IHC result (HPA: tissue IHC; UniProt P08311). |
| Q: Does an IF/ICC punctate signal confirm the IHC pattern? (HPA: no ICC-IF images listed). | HPA supplies no ICC-IF image set or main subcellular location for this record, so an IF pattern lacks the supplied image-based validation (HPA: subcellular record). | A: Interpret IF/ICC separately, with localization and antibody controls; granule or lysosome localization is biologically plausible but does not itself validate an IF image (UniProt P08311: subcellular location; general IF practice). |
Experiment evidence
IHC & IF images showing CTSG staining
PB10053 · IHCIHC analysis of Cathepsin G/CTSG using anti-Cathepsin G/CTSG antibody (PB10053). Cathepsin G/CTSG was detected in a paraffin-embedded sectio
HPA · Cerebral cortexHuman Protein Atlas IHC, Cerebral cortex. Source: https://www.proteinatlas.org/ENSG00000100448-CTSG/tissue/cerebral+cortex#imid_15150298
HPA · ColonHuman Protein Atlas IHC, Colon. Source: https://www.proteinatlas.org/ENSG00000100448-CTSG/tissue/colon#imid_15150232
HPA · LiverHuman Protein Atlas IHC, Liver. Source: https://www.proteinatlas.org/ENSG00000100448-CTSG/tissue/liver#imid_15150225
HPA · KidneyHuman Protein Atlas IHC, Kidney. Source: https://www.proteinatlas.org/ENSG00000100448-CTSG/tissue/kidney#imid_15150226
← swipe / scroll for more images →
Real IHC / IF data behind the staining-pattern expectations in this section.
Sample controls for CTSG IHC & IF
🧪Run bone marrow first: hematopoietic cells should stain strongly (HPA: High in bone marrow hematopoietic cells). Use adipose tissue as the negative tissue, focusing on adipocytes (HPA: Not detected in adipocytes); on the marrow slide, assess morphologically nonhematopoietic cells as internal negative cells, without assuming every hematopoietic cell must stain (HPA: High in hematopoietic cells).
Positive control tissue: Bone marrow (Hematopoietic cells, HPA High)
Negative control tissue: Adipose tissue (HPA Not detected)
ICC-IF cell lines (HPA subcellular resource): HPA carries no ICC-IF cell line for CTSG; derive a cell-line control from the positive tissue's cell type (Hematopoietic cells) and confirm it by RNA or western blot first.
Technical controls: Include a no-primary, secondary-only control and a rabbit IgG isotype control matched to the primary’s concentration and clonality where applicable; use a CTSG knockout specimen or validated immunizing-peptide block if available (PB10053 caption: rabbit primary; standard IHC control practice). Quench endogenous peroxidase in bone marrow and check the no-primary slide for residual DAB signal (PB10053 caption: HRP/DAB; standard IHC practice).
⚠️Feasibility: The selected PB10053 paraffin-section caption uses heat retrieval in EDTA at pH 8.0, but does not establish that retrieval is required; its fixative and any CTSG-specific fixation window or effect are unreported (PB10053 caption). The supplied evidence does not establish frozen sections or IF/ICC as easier than paraffin IHC, and HPA lists no ICC-IF images for CTSG (PB10053 caption; HPA subcellular). In bone marrow, endogenous peroxidase can cause HRP/DAB background, while secreted CTSG may complicate cell-specific scoring (standard IHC practice; UniProt P08311: secretion by activated neutrophils).
HPA tissue IHC evidence for CTSG
Comprehensive Human Protein Atlas IHC scoring per tissue (reliability: Enhanced — High consistency between antibody staining and RNA expression data.). Rows are taken directly from the HPA tissue chart — click any row's HPA link to view the source.
Positive expression · recommended positive controls
| Tissue | Cell type | Level | Evidence | Source |
|---|---|---|---|---|
| Bone marrow | Hematopoietic cells | High | Protein (IHC) | HPA → |
| Lymph node | Non-germinal center cells | Medium | Protein (IHC) | HPA → |
| Spleen | Cells in red pulp | Medium | Protein (IHC) | HPA → |
| Tonsil | Non-germinal center 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 → |
| Breast | Adipocytes | Not detected | Protein (IHC) | HPA → |
| Bronchus | Respiratory epithelial cells | Not detected | Protein (IHC) | HPA → |
Section 3
Advanced CTSG IHC Tips
Troubleshoot CTSG staining in paraffin sections by checking retrieval, cell identity, compartment, controls, and scoring before interpreting signal.
Which retrieval condition should I start with for CTSG in paraffin sections?
Start with heat-mediated retrieval in EDTA pH 8.0 for paraffin sections (datasheet PB10053). The selected tonsil image used that condition before incubation with 2 μg/ml primary antibody overnight at 4°C, providing a matched starting workflow (datasheet PB10053). If staining is weak, compare a small retrieval time series while keeping section thickness, antibody concentration, and detection conditions constant (standard IHC practice). Excessive heating can damage morphology or increase nonspecific staining, so assess both signal and tissue preservation on each slide (standard IHC practice). Use known positive and negative cell populations when judging whether a retrieval change improved CTSG detection (HPA tissue IHC; standard IHC practice).
How should I troubleshoot weak CTSG staining when fixation details are missing?
The selected paraffin-section caption does not state a fixative, so CTSG-specific fixation sensitivity is unknown for this antibody (datasheet PB10053). Record the fixative, fixation duration, and processing history for each specimen, then compare sections processed together before changing the antibody concentration (standard IHC practice). Keep retrieval at EDTA pH 8.0 initially and use the caption’s 2 μg/ml overnight incubation as a reference condition (datasheet PB10053). If specimens differ in signal, assess morphology and a known positive control from the same processing batch before attributing the difference to CTSG abundance (standard IHC practice). Do not infer a fixation effect from tissue staining patterns alone (HPA tissue IHC; standard IHC practice).
Where should convincing CTSG staining appear within positive cells?
Expect predominantly cytoplasmic staining in the relevant cell subsets when reading tissue sections (HPA tissue IHC: selective cytoplasmic expression). CTSG is also annotated in cytoplasmic granules and lysosomes, so a granular cytoplasmic pattern is biologically plausible (UniProt P08311: subcellular locations). Secreted CTSG may produce extracellular signal, while nuclear localisation has been reported during apoptosis; neither pattern alone establishes the source cell (UniProt P08311: secretion and apoptotic localisation). Compare the staining with cell morphology and adjacent negative cells before assigning a compartment or lineage (standard IHC practice). In tonsil, focus interpretation on non-germinal center cells rather than treating uniform staining of all cells as expected (HPA tissue IHC: tonsil).
Could CTSG processing or glycosylation explain a changed staining pattern?
The record lists 0 isoforms, so an isoform switch is not a supported explanation for different tissue staining (UniProt P08311: isoforms). CTSG is processed from a 255-aa precursor to chains spanning residues 21–244 or 21–243, and glycosylation is annotated at residue 71 (UniProt P08311: processing and glycosylation). Without a mapped antibody epitope, those features cannot establish which molecular form the stain detects (UniProt P08311; standard IHC practice). If staining changes after processing, compare matched sections under the same EDTA pH 8.0 retrieval and antibody conditions (datasheet PB10053; standard IHC practice). Treat a compartment shift as an observation to validate, rather than evidence of a particular processed form (standard IHC practice).
How can I check a CTSG IHC pattern with multiplex immunofluorescence?
Use IF as a separate validation experiment and pair CTSG with a validated neutrophil marker, since CTSG protein is reported in neutrophils (UniProt P08311: tissue specificity; standard IF practice). Select fluorophores after checking the specimen’s autofluorescence, and include single-stain controls to distinguish channel bleed-through from colocalisation (standard IF practice). For an intracellular CTSG epitope, optimise permeabilisation after fixation; the record lists cytoplasmic granules and lysosomes, but the antibody’s epitope is not supplied (UniProt P08311: subcellular locations; standard IF practice). If an epitope is extracellular, assess access without assuming that intracellular permeabilisation is required (UniProt P08311: secretion and no transmembrane segment; standard IF practice). Compare cell-level IF findings with the chromogenic pattern, keeping the assays’ detection methods distinct (standard IHC/IF practice).
What should I check when CTSG DAB staining is widespread?
First inspect a no-primary control for signal from the detection system, including endogenous peroxidase, before interpreting widespread DAB as CTSG (standard IHC practice). The selected tonsil workflow used 10% goat serum block and a peroxidase-conjugated secondary with DAB, so reproduce its blocking and detection conditions during troubleshooting (datasheet PB10053). Apply an appropriate peroxidase block and compare primary-antibody titrations around the documented 2 μg/ml condition (datasheet PB10053; standard IHC practice). Check whether signal follows cytoplasmic cell subsets rather than appearing uniformly across tissue or along section edges (HPA tissue IHC: staining profile; standard IHC practice). Keep development and counterstaining consistent across comparison slides (standard IHC practice).
How should I quantify CTSG-positive cells in chromogenic sections? ⚠ ANSWER MARKED FOR VERIFICATION
Define the cell population and tissue region before scoring, then report the percentage of CTSG-positive cells and staining intensity within that population (standard IHC practice). An H-score combines intensity categories with their positive-cell percentages on a 0–300 scale; use the same thresholds for every slide (standard IHC practice). For spatial comparisons, report positive-cell density per mm² of viable tissue and normalise counts to the measured viable area (standard IHC practice). In tonsil, analyse non-germinal center cells separately from other compartments because their reported CTSG staining differs (HPA tissue IHC: tonsil; standard IHC practice). State the scoring unit and assess slides with matched staining and imaging settings (standard IHC practice).
How do I distinguish true CTSG positivity from staining artefacts?
Prioritise cell-associated cytoplasmic staining in plausible populations: CTSG is reported in neutrophils, and tissue IHC shows selective cytoplasmic staining in lymphoid and hematopoietic subsets (UniProt P08311: tissue specificity; HPA tissue IHC: staining profile). Check unexpected nuclear signal against apoptotic morphology, because nuclear CTSG has been reported during apoptosis (UniProt P08311: apoptotic localisation; standard IHC practice). Treat edge staining, necrotic regions, and signal persisting in a no-primary control as possible artefacts, including endogenous enzyme activity (standard IHC practice). Extracellular staining may be compatible with secretion by activated neutrophils, but does not identify the producing cell (UniProt P08311: secretion; standard IHC practice). Confirm disputed patterns with morphology, compartment controls, and a matched positive section (standard IHC practice).
Boster reagents
Best CTSG / Cathepsin G IHC Antibodies
The catalog includes human-reactive IHC antibodies, with a paraffin-section image for PB10053 in human tonsil (catalog; PB10053 image caption). PB9049 also lists rat reactivity (catalog). No IF data are provided (catalog).
Real IHC data
Anti-Cathepsin G/CTSG Antibody ®
Cat # PB10053
PB10053 is listed for human IHC and has an image from a paraffin-embedded human tonsil section; its fixative is unreported (catalog; PB10053 image caption). PB9049 lists IHC and human and rat reactivity, but has no IHC image in the payload (catalog).
Which to pick: For tissue IHC, choose PB10053 when the documented human tonsil paraffin-section example is relevant; the caption does not report the fixative (PB10053 image caption). Neither SKU lists IF/ICC, so neither has supporting IF/ICC data here (catalog). For cross-species planning, PB9049 lists human and rat reactivity, though its IHC entry specifies human and no rat IHC image is provided (catalog; PB9049 dilution entry).
Each figure is that product's own IHC / IF validation image from its datasheet.
References
- UniProt Consortium. UniProt entry P08311 (CATG_HUMAN, Cathepsin G).
- Human Protein Atlas. CTSG tissue IHC expression (reliability: Enhanced).
- Human Protein Atlas. CTSG subcellular location (ICC-IF): Highest expression in THP-1: 6931.7 nTPM.
- Human Protein Atlas. CTSG antibody validation summary (2 antibodies).
- CTSG may inhibit disease progression in HIV-related lung cancer patients by affecting immunosuppression. Infectious agents and cancer 2024 — PMC11290089.
- Cathepsin G promotes arteriovenous fistula maturation by positively regulating the MMP2/MMP9 pathway. Renal failure 2024 — PMC10878333.
- Construction of a new predictive model in head and neck squamous cell carcinoma based on the investigation of extracellular matrix-associated genes. Oncology letters 2026 — PMC13563026.
- The intratumour microbiota and neutrophilic inflammation in squamous cell vulvar carcinoma microenvironment. Journal of translational medicine 2023 — PMC10141905.
- PubMed PMID:3304423 — UniProt-cited evidence.
- PubMed PMID:2569462 — UniProt-cited evidence.
- PubMed PMID:15489334 — UniProt-cited evidence.
Immunohistochemistry protocol sheet for CTSG (Cathepsin G). Expected localisation Selective cytoplasmic staining in lymphoid and hematopoietic cells (HPA tissue IHC). Antigen retrieval: EDTA pH 8.0 HIER, heat-mediated (datasheet PB10053). Validated IHC antibody: PB10053 at 2-5μg/ml (the product's own IHC validation image is shown). Controls (HPA): positive Bone marrow (Hematopoietic cells); negative Adipose tissue. IHC-P workflow on paraffin sections; fixative unspecified. Protocol steps: 1. Sample: Paraffin-embedded human tonsil tissue; fixative not specified (datasheet PB10053); 2. Fixation: Image fixative and duration unreported (datasheet PB10053); 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 PB10053); 20 min, 95–100 °C (standard); 6. Peroxidase block: 3% H2O2, 10 min , room temperature (standard); 7. Blocking: 10% goat serum (datasheet PB10053); 8. Primary antibody: Rabbit anti-CTSG, 2-5μg/ml (datasheet PB10053); 9. Primary incubation: Overnight at 4 °C (datasheet PB10053). Watch for: Fixation: Keep fixation consistent across paraffin sections. (standard IHC practice; not target-specific); Caveat: Secretion by activated neutrophils may obscure the cell of origin (UniProt); Isoform / epitope: No isoforms reported; cleaved propeptides may alter epitope detection (UniProt); Regulation: Neutrophil activation promotes secretion (UniProt). Evidence: UniProt P08311, HPA tissue IHC · Enhanced, HPA cell-line RNA · Highest expression in THP-1: 6931.7 nTPM, Datasheet PB10053, PMC11290089, PMC10878333. QR code links to https://www.bosterbio.com/bosterbio-gene-info-cards/CTSG/immunohistochemistry-ihc-guide.