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KYNU / Kynureninase · IHC design guide
Design Immunohistochemistry for KYNU
Plan KYNU staining in paraffin sections using hepatocytes and renal tubules as high-expression references (HPA tissue IHC). Assess cytoplasmic staining by cell type and keep fixation consistent across sections (HPA tissue IHC; standard IHC practice).
Evidence assembled Oct 2026 · For research use; verify linked source records and product datasheet before use
KYNU 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 staining in several tissues (HPA tissue IHC) | |
| Staining pattern | Cytoplasmic signal in hepatocytes, renal tubules and lung macrophages (HPA tissue IHC) | |
| Antigen retrieval | Citrate pH 6.0 HIER, 95–98 °C, 20 min (rule: cytoplasmic / membrane antigen) | |
| Positive control | Kidney+4 more · see all | |
| Negative control | Bone marrow+4 more · see all |
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 | Staining and RNA show medium consistency; verify signal (HPA tissue IHC) | |
| Regulation | Abundance varies by cell type (HPA tissue IHC) | |
| Isoform / epitope | 2 isoforms; epitope coverage is unspecified (UniProt) |
Section 1
Recommended KYNU IHC & IF Protocols
The catalog antibody’s IHC-P protocol is accompanied by published KYNU IHC conditions for nevus, melanoma, lung adenocarcinoma, and other tissue sections (PMC9329910; PMC9139317; PMC7590459).
| Sample | Paraffin-embedded mouse heart tissue; fixative not specified (datasheet A06885) |
| Fixation | Image fixative and duration unreported (datasheet A06885); 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-KYNU, 1:50-1:100 (datasheet A06885) |
| 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 | KYNU-positive staining in cells in tubules of kidney (HPA tissue IHC: High). HPA tissue profile: Cytoplasmic expression in several tissues, high expression in hepatocytes, renal tubules and lymphoid tissues. No signal in the no-primary control. |
💡Decision noteStart with citrate pH 6.0 heat retrieval at 95–98 °C for 20 min (page antigen-retrieval specification).
Section 2
What Is the Expected KYNU Staining Pattern?
KYNU is a cytosolic protein with no transmembrane segment (UniProt Q16719). In paraffin-section IHC, expect cytoplasmic staining, particularly in hepatocytes, renal tubular cells, lung macrophages and placental trophoblastic cells (HPA tissue IHC). HPA rates tissue staining reliability Enhanced, while noting medium consistency with RNA data and pending external verification (HPA tissue IHC).
| Strong cytoplasmic staining in hepatocytes or renal tubular cells (HPA tissue IHC). | This matches two HPA High patterns and KYNU’s cytosolic location (HPA tissue IHC; UniProt Q16719). Assess the named cells, since staining across an entire section can obscure whether the expected cells are positive (general IHC practice). |
| Predominantly nuclear staining with little cytoplasmic signal. | This does not match the principal IHC pattern (HPA tissue IHC). HPA reports an uncertain nucleoplasmic location in ICC-IF, so nuclear signal alone cannot establish KYNU localisation (HPA subcellular). Check controls and detection background (general IHC practice). |
| Strong staining in cells reported as undetected, such as bone-marrow hematopoietic cells (HPA tissue IHC). | The cell assignment conflicts with HPA’s observation and warrants a specificity check (HPA tissue IHC). Cross-reactivity or endogenous detection activity are possible explanations, not conclusions from this slide alone (general IHC practice). |
| Weak, diffuse colour across cells and surrounding tissue, without a clear cytoplasmic pattern. | This is difficult to score as KYNU when expected positive cells cannot be distinguished (HPA tissue IHC; general IHC practice). Compare a no-primary control and review blocking, washing and detection conditions (general IHC practice). |
| No staining in hepatocytes or renal tubular cells (HPA tissue IHC). | A blank known-positive cell population makes this IHC run inconclusive (HPA tissue IHC; general IHC practice). Review tissue identity, antibody and detection steps before interpreting an unstained test specimen as KYNU-negative (general IHC practice). |
💡Expected KYNU appearanceCall the IHC result positive when distinct cytoplasmic staining is strong in hepatocytes or renal tubular cells (HPA tissue IHC; UniProt Q16719); predominantly nuclear colour or widespread cell-independent colour calls for control review (HPA subcellular; general IHC practice).
| Cell type and tissue choice (HPA tissue IHC). | HPA reports High staining in hepatocytes, renal tubular cells, lung macrophages, placental trophoblastic cells and tonsillar non-germinal center cells; other cells in those tissues need separate interpretation (HPA tissue IHC). |
| Evidence strength (HPA tissue IHC; HPA antibodies). | The listed antibody HPA031686 has Enhanced IHC validation (HPA antibodies). HPA also describes medium agreement between tissue staining and RNA data, with external verification pending; an individual section still needs controls (HPA tissue IHC; general IHC practice). |
| Compartment and topology (UniProt Q16719; HPA subcellular). | KYNU is cytosolic and has no transmembrane segment (UniProt Q16719). HPA’s ICC-IF evidence supports cytosol, while its additional nucleoplasmic assignment is uncertain; avoid making nuclear staining the primary IHC criterion (HPA subcellular). |
| Isoforms and antibody coverage (UniProt Q16719). | UniProt lists two KYNU isoforms (UniProt Q16719). The supplied evidence gives no antibody epitope or isoform-specific IHC performance, so an unexpected staining pattern cannot be assigned to either isoform from these records. |
| Situation | Likely cause | Next action |
|---|---|---|
| Known-positive liver or kidney cells are blank (HPA tissue IHC). | An IHC run or specimen problem is possible; HPA’s High pattern does not identify which step failed (HPA tissue IHC; general IHC practice). | Verify tissue and cell identity, then check the antibody, retrieval and detection steps against the chosen IHC-P procedure (general IHC practice). |
| A chromogenic deposit appears broadly, including where cells lack the expected cytoplasmic pattern. | Endogenous detection activity or nonspecific reagent binding may contribute (general IHC practice). | Compare no-primary and reagent controls; review blocking, washing and, if applicable, endogenous enzyme blocking (general IHC practice). |
| Colour is mainly nuclear. | The principal KYNU location is cytosolic; an additional nucleoplasmic ICC-IF location is uncertain (UniProt Q16719; HPA subcellular). | Recheck localisation in a High-staining HPA cell type and inspect controls before accepting a nuclear IHC result (HPA tissue IHC; general IHC practice). |
| Unexpected cells stain strongly in an otherwise plausible section. | HPA levels are cell-specific; for example, bone-marrow hematopoietic cells are reported as Not detected (HPA tissue IHC). | Score the actual cell population, compare an HPA High reference population and use detection controls to investigate unexpected colour (HPA tissue IHC; general IHC practice). |
| A weak sample is being called negative. | HPA reports Low staining in some epithelia, including bronchial respiratory and colonic glandular cells (HPA tissue IHC). | Compare the sample with a High reference cell type in the same run and record intensity by cell type before assigning a negative score (HPA tissue IHC; general IHC practice). |
| Can IF/ICC show nuclear KYNU? | HPA supports cytosol as the main ICC-IF location and marks the additional nucleoplasmic location uncertain (HPA subcellular). | Treat cytosolic signal as the primary expectation, assess nuclear signal with controls and use the separate IF/ICC guide for assay setup (HPA subcellular; general IF practice). |
Experiment evidence
IHC & IF images showing KYNU staining
A06885 · IHCImmunohistochemistry of paraffin-embedded mouse heart using KYNU antibody at dilution of 1:100 .Perform microwave antigen retrieval with 10
HPA · Cerebral cortexHuman Protein Atlas IHC, Cerebral cortex. Source: https://www.proteinatlas.org/ENSG00000115919-KYNU/tissue/cerebral+cortex#imid_8142256
HPA · ColonHuman Protein Atlas IHC, Colon. Source: https://www.proteinatlas.org/ENSG00000115919-KYNU/tissue/colon#imid_8142188
HPA · LiverHuman Protein Atlas IHC, Liver. Source: https://www.proteinatlas.org/ENSG00000115919-KYNU/tissue/liver#imid_8142173
HPA · KidneyHuman Protein Atlas IHC, Kidney. Source: https://www.proteinatlas.org/ENSG00000115919-KYNU/tissue/kidney#imid_8142174
HPA · ICC-IF A-549Human Protein Atlas immunofluorescence, A-549, antibody HPA031686; green = KYNU, blue = nucleus, red = microtubules.
HPA · ICC-IF A-549Human Protein Atlas immunofluorescence, A-549, antibody HPA031686; green = KYNU, blue = nucleus, red = microtubules.
← swipe / scroll for more images →
Real IHC / IF data behind the staining-pattern expectations in this section.
Sample controls for KYNU IHC & IF
🧪Run kidney first: tubular cells should show strong KYNU staining (HPA: High in kidney tubular cells). Use bone marrow hematopoietic cells as the negative tissue (HPA: Not detected); on the kidney slide, use non-tubular cells as internal background comparators only if they show counterstain without comparable cytoplasmic signal, since their KYNU status is not specified by the supplied HPA row (HPA: High in kidney tubular cells; UniProt Q16719: cytosol).
Positive control tissue: Kidney (Cells in tubules, HPA High)
Negative control tissue: Bone marrow (HPA Not detected)
ICC-IF cell lines (HPA subcellular resource): HPA ICC-IF images show KYNU in A-549, HeLa, SiHa, with annotated localisation: Cytosol (supported) (HPA subcellular).
Technical controls: Include a no-primary, secondary-only control and an isotype control matched to the primary antibody’s host species and clonality; use KYNU-knockout material as a biological negative where available (standard IHC practice). For chromogenic kidney IHC, quench endogenous peroxidase and check the no-primary slide for residual tubular signal (standard IHC practice).
⚠️Feasibility: A target-specific fixation window or fixation effect is unreported in the supplied evidence, and the selected paraffin-section mouse-heart caption does not state its fixative (A06885 tissue-IHC caption). That caption uses microwave retrieval in 10 mM PBS, pH 7.2, before staining at 1:100; it does not establish that retrieval is required for KYNU (A06885 tissue-IHC caption). The supplied evidence does not establish whether frozen sections or IF are easier; in kidney IHC, endogenous peroxidase can create tubular background that requires control-slide assessment (standard IHC practice).
HPA tissue IHC evidence for KYNU
Comprehensive Human Protein Atlas IHC scoring per tissue (reliability: Enhanced — 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 |
|---|---|---|---|---|
| Kidney | Cells in tubules | High | Protein (IHC) | HPA → |
| Liver | Hepatocytes | High | Protein (IHC) | HPA → |
| Lung | Macrophages | High | Protein (IHC) | HPA → |
| Placenta | Trophoblastic cells | High | Protein (IHC) | HPA → |
| Tonsil | Non-germinal center cells | High | Protein (IHC) | HPA → |
Undetected expression · recommended negative controls
| Tissue | Cell type | Level | Evidence | Source |
|---|---|---|---|---|
| Bone marrow | Hematopoietic cells | Not detected | Protein (IHC) | HPA → |
| Cerebellum | Cells in granular layer | Not detected | Protein (IHC) | HPA → |
| Epididymis | Glandular cells | Not detected | Protein (IHC) | HPA → |
| Fallopian tube | Glandular cells | Not detected | Protein (IHC) | HPA → |
| Hippocampus | Glial cells | Not detected | Protein (IHC) | HPA → |
Section 3
Advanced KYNU IHC Tips
Troubleshoot KYNU chromogenic IHC in paraffin sections by checking retrieval, staining location, tissue controls and scoring before interpreting signal.
How should I retrieve KYNU in paraffin sections when staining is weak?
Start with citrate buffer at pH 6.0, heated to 95–98 °C for 20 min (page retrieval protocol). If cytoplasmic staining remains weak, compare a matched section using microwave retrieval in 10 mM PBS, pH 7.2, the condition reported for the catalog antibody in paraffin-embedded mouse heart (A06885 caption). Keep antibody dilution, detection and development time constant across the comparison so retrieval is the variable being assessed (standard IHC practice). Judge improvement by clearer cytoplasmic signal and preserved tissue morphology, using a negative control to detect retrieval-associated background (UniProt Q16719 localisation; standard IHC practice).
Could fixation explain weak or uneven KYNU staining?
KYNU-specific sensitivity to fixation is unknown because no target-specific fixation evidence is supplied (provided fixation evidence). The catalog image describes paraffin-embedded mouse heart but does not state its fixative, so its staining cannot establish how KYNU responds to a particular fixation condition (A06885 caption). For a controlled comparison, process replicate specimens with recorded fixation conditions, then stain matched sections using identical retrieval, antibody dilution and chromogenic development (standard IHC practice). Include a tissue control expected to show cytoplasmic KYNU, such as liver hepatocytes, and assess morphology alongside signal before attributing a difference to fixation (HPA: High in hepatocytes; UniProt Q16719 localisation; standard IHC practice).
What staining pattern should I expect, and how should I assess nuclear signal?
Expect predominantly cytoplasmic staining because KYNU is a cytosolic protein without an annotated transmembrane segment (UniProt Q16719 localisation and topology). HPA reports mainly cytosolic localisation and an additional nucleoplasmic location with uncertain support, so isolated nuclear chromogen needs particular scrutiny (HPA subcellular). Compare nuclear and cytoplasmic staining within the same intact cells, then check a no-primary control for detection-related nuclear colour (standard IHC practice). Use cell identity and morphology as additional checks: hepatocytes and renal tubular cells have reported high KYNU staining, whereas a nuclear-only pattern across unrelated cells does not match the predominant localisation evidence (HPA tissue IHC; UniProt Q16719 localisation).
Can this stain distinguish KYNU isoforms or reveal epitope masking?
KYNU has 2 listed isoforms, but the supplied antibody evidence does not map its epitope or establish isoform discrimination (UniProt Q16719 isoforms; supplied antibody evidence). Therefore, report staining as KYNU immunoreactivity rather than assigning signal to isoform 1 or 2 (UniProt Q16719 isoforms; standard IHC interpretation). If staining is unexpectedly absent, compare the page retrieval condition with the catalog image’s 10 mM PBS, pH 7.2 microwave condition on matched sections before proposing epitope masking (page retrieval protocol; A06885 caption). The annotated pyridoxal phosphate-linked lysine at position 276 does not establish whether this antibody recognises a modified epitope (UniProt Q16719 modified residues; supplied antibody evidence).
How should I check KYNU localisation by multiplex IF?
For the separate IF/ICC application, pair KYNU with a validated marker for the cell population under examination, such as a macrophage marker when examining lung macrophages (HPA: High in macrophages; standard IF practice). Select a fluorophore in a channel with low measured tissue autofluorescence, and include single-colour and no-primary controls to assess bleed-through and background (standard IF practice). KYNU is cytosolic and has no annotated transmembrane segment, so use permeabilisation appropriate for an intracellular epitope rather than treating it as a cell-surface target (UniProt Q16719 localisation and topology; standard IF practice). Interpret nucleoplasmic overlap cautiously because that additional location has uncertain support (HPA subcellular).
How can I separate KYNU signal from diffuse chromogenic background?
First inspect a no-primary control and a section processed without chromogen to locate detection-related colour and native pigment before changing the KYNU antibody condition (standard IHC practice). In a peroxidase-based workflow, apply an endogenous peroxidase block and use a timed DAB development step; these are general chromogenic IHC measures, not KYNU-specific validation (standard IHC practice). If background rises throughout the section, compare stronger blocking, more thorough washes and a lower antibody concentration against the catalog image’s 1:100 dilution (A06885 caption; standard IHC practice). Preserve a positive tissue control and look for cytoplasmic signal in expected cells when deciding whether background reduction also removed useful staining (HPA tissue IHC; UniProt Q16719 localisation).
What is a defensible way to quantify KYNU staining across sections? ⚠ ANSWER MARKED FOR VERIFICATION
Define the cell population and region before scoring, then record the percentage of positive cells and staining intensity to calculate an H-score from 0–300 (standard IHC scoring practice). For heterogeneous infiltrates, report positive-cell density per mm² alongside the fraction of eligible cells that stain, keeping cell identification consistent across sections (standard IHC quantification practice). Normalise comparisons to the same cell type and sampled viable tissue area rather than whole-section colour, because HPA reports different expression levels among hepatocytes, renal tubules and lung macrophages (HPA tissue IHC; standard IHC quantification practice). Apply identical thresholds, retrieval and chromogen development to all compared sections (standard IHC practice).
When should I doubt an apparent KYNU-positive result?
A credible KYNU-positive cell should show interpretable cytoplasmic staining in preserved tissue, consistent with its supported cytosolic localisation (UniProt Q16719 localisation; HPA subcellular). Compare the cell type with reported patterns: hepatocytes, renal tubular cells and lung macrophages are high, while several other populations are reported as not detected (HPA tissue IHC). Treat staining limited to section edges, necrotic areas or unexpected compartments as suspect, and inspect matched negative controls for handling artefacts or endogenous enzyme activity (standard IHC practice). HPA tissue reliability is Enhanced but notes only medium staining–RNA consistency and pending external verification, so corroborate consequential findings with independent evidence (HPA tissue IHC reliability).
Boster reagents
Best KYNU / Kynureninase IHC Antibodies
Anti-KYNU antibodies list IHC and IF/ICC use in human, mouse, and rat; real IHC data show paraffin-embedded mouse heart, while no IF image is provided (catalog applications/reactivity; A06885 image captions).
Real IHC data
Anti-Kynureninase KYNU Antibody
Cat # A06885
A06885 is the sole rendered card; its own figure documents IHC on paraffin-embedded mouse heart at 1:100 after microwave antigen retrieval in 10 mM PBS, pH 7.2 (A06885 IHC caption). A06885 also lists IF/ICC and human, mouse, and rat reactivity, but has no IF figure in the payload (A06885 catalog applications/reactivity; A06885 IF image alts).
Which to pick: Choose A06885 for paraffin-section IHC because its own figure shows mouse heart staining; the caption does not report the fixative (A06885 IHC caption). For IF/ICC, both A06885 and A06885-1 list those applications, but neither provides an IF image; both are rabbit antibodies with no clone specified (catalog applications/host/clone; IF image alts). For cross-species planning, either SKU lists human, mouse, and rat reactivity, while only A06885 supplies its own tissue IHC figure (catalog reactivity; IHC image alts).
Each figure is that product's own IHC / IF validation image from its datasheet.
References
- UniProt Consortium. UniProt entry Q16719 (KYNU_HUMAN, Kynureninase).
- Human Protein Atlas. KYNU tissue IHC expression (reliability: Enhanced).
- Human Protein Atlas. KYNU subcellular location (ICC-IF): Mainly localized to the cytosol. In addition localized to the nucleoplasm..
- Human Protein Atlas. KYNU antibody validation summary (1 antibodies).
- Differential Gene Expression and Methylation Analysis of Melanoma in TCGA Database to Further Study the Expression Pattern of KYNU in Melanoma. Journal of personalized medicine 2022 — PMC9329910.
- Mutational Activation of the NRF2 Pathway Upregulates Kynureninase Resulting in Tumor Immunosuppression and Poor Outcome in Lung Adenocarcinoma. Cancers 2022 — PMC9139317.
- Kynureninase Upregulation Is a Prominent Feature of NFR2-Activated Cancers and Is Associated with Tumor Immunosuppression and Poor Prognosis. Cancers 2023 — PMC9913753.
- Differential kynurenine pathway metabolism in highly metastatic aggressive breast cancer subtypes: beyond IDO1-induced immunosuppression. Breast cancer research : BCR 2020 — PMC7590459.
- PubMed PMID:8706755 — UniProt-cited evidence.
- PubMed PMID:9180257 — UniProt-cited evidence.
- PubMed PMID:14702039 — UniProt-cited evidence.
Immunohistochemistry protocol sheet for KYNU (Kynureninase). Expected localisation Cytoplasmic staining in several tissues (HPA tissue IHC). Antigen retrieval: Citrate pH 6.0 HIER, 95–98 °C, 20 min (rule: cytoplasmic / membrane antigen). Validated IHC antibody: A06885 at 1:50-1:100 (the product's own IHC validation image is shown). Controls (HPA): positive Kidney (Cells in tubules); negative Bone marrow. IHC workflow; specimen preparation unspecified. Protocol steps: 1. Sample: Paraffin-embedded mouse heart tissue; fixative not specified (datasheet A06885); 2. Fixation: Image fixative and duration unreported (datasheet A06885); 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-KYNU, 1:50-1:100 (datasheet A06885); 9. Primary incubation: Overnight at 4 °C (standard). Watch for: Fixation: Keep fixation conditions consistent across sections. (standard IHC practice; not target-specific); Caveat: Staining and RNA show medium consistency; verify signal (HPA tissue IHC); Isoform / epitope: 2 isoforms; epitope coverage is unspecified (UniProt); Regulation: Abundance varies by cell type (HPA tissue IHC). Evidence: UniProt Q16719, HPA tissue IHC · Enhanced, HPA ICC-IF · Mainly localized to the cytosol. In addition localized to the…, Datasheet A06885, PMC9329910, PMC9139317. QR code links to https://www.bosterbio.com/bosterbio-gene-info-cards/KYNU/immunohistochemistry-ihc-guide.