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XRCC5 / DNA repair protein Ku80 · IHC design guide
Design Immunohistochemistry for XRCC5
Plan XRCC5 chromogenic IHC in paraffin sections using its observed widespread nuclear tissue staining as a reference (HPA tissue IHC). The guide covers fixation consistency, staining controls and nuclear scoring, including the reported lack of signal in liver cholangiocytes (HPA tissue IHC).
Evidence assembled Oct 2026 · For research use; verify linked source records and product datasheet before use
XRCC5 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 | Nuclear tissue staining (HPA tissue IHC); nucleolar and chromosomal locations are annotated (UniProt) | |
| Staining pattern | Widespread nuclear staining across tissue cell types (HPA tissue IHC) | |
| Antigen retrieval | EDTA pH 8.0 HIER, heat-mediated (datasheet PA1641) | |
| Positive control | Appendix+4 more · see all | |
| Negative control | Liver |
Important caveats
Reasons your staining may differ from the expected pattern.
| Fixation | Keep fixation consistent across paraffin sections (standard IHC practice; not target-specific); Matched tissue-IHC evidence does not establish the fixation claim. Validate the specimen-specific method before use. (selected-SKU IHC image PA1641) | |
| Caveat | Liver cholangiocytes show no detected signal (HPA tissue IHC) | |
| Regulation | Low tissue specificity (HPA tissue RNA) | |
| Isoform / epitope | No annotated isoforms; chain spans residues 2–732 (UniProt) |
Section 1
Recommended XRCC5 IHC & IF Protocols
The catalog antibody’s IHC-P protocol uses EDTA pH 8.0 retrieval (datasheet: PA1641). Four published XRCC5 IHC workflows provide sample-specific comparisons (PMC5648251; PMC8762376; PMC5354834; PMC6137920).
| Sample | Paraffin-embedded human intestinal cancer tissue; fixative not specified (datasheet PA1641) |
| Fixation | Image fixative and duration unreported (datasheet PA1641); 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 PA1641); 20 min, 95–100 °C (standard) |
| Peroxidase block | 3% H2O2, 10 min, room temperature (standard) |
| Blocking | 10% goat serum (datasheet PA1641) |
| Primary antibody | Rabbit anti-XRCC5, 0.5-1μg/ml (datasheet PA1641) |
| Primary incubation | Overnight at 4 °C (datasheet PA1641) |
| Detection | Streptavidin-biotin complex (SABC), DAB chromogen (datasheet PA1641) |
| Counterstain | Hematoxylin, blue, dehydrate and mount (standard) |
| Expected result | XRCC5-positive staining in endocrine cells of appendix (HPA tissue IHC: High). HPA tissue profile: Ubiquitous nuclear expression. No signal in the no-primary control. |
💡Decision noteTry EDTA pH 8.0 heat retrieval first with the catalog antibody (datasheet: PA1641). Sodium citrate, 10 mM, microwaved for 4 min, is a published alternative (PMC5648251: IHC methods).
Section 2
What Is the Expected XRCC5 Staining Pattern?
XRCC5 is a nuclear protein associated with the nucleolus and chromosomes (UniProt P13010: subcellular location). In paraffin-section IHC, expect widespread nuclear staining; HPA describes ubiquitous nuclear expression with Supported reliability and medium consistency between antibody staining and RNA expression (HPA: tissue IHC). XRCC5 has no transmembrane segment, so a membrane-rim pattern is unexpected (UniProt P13010: topology). Judge intensity against the cell types documented in the tissue being examined (HPA: tissue IHC).
| Distinct nuclear staining in breast glandular cells or bone-marrow hematopoietic cells (HPA: High in each cell type). | This matches documented high-staining examples and XRCC5’s nuclear location (HPA: tissue IHC; UniProt P13010: subcellular location). Compare nuclei with nearby tissue structure and the run controls before calling intensity, since HPA’s IHC reliability is Supported with medium staining–RNA consistency (HPA: tissue IHC). |
| Predominantly membrane-rim or diffuse cytoplasmic staining, with little nuclear signal. | The compartment conflicts with XRCC5’s nuclear annotation and lack of a transmembrane segment (UniProt P13010: subcellular location and topology). Treat it as a possible nonspecific or detection artefact, then review the primary-antibody omission control and staining distribution (general IHC practice). |
| Strong staining appears in liver cholangiocytes while nuclei in documented high-staining cells are weak. | HPA reports cholangiocytes as Not detected, whereas several other cell types are High (HPA: tissue IHC). This mismatch raises possible cross-reactivity or endogenous detection activity; it does not prove either cause or establish that all liver cells lack XRCC5 (HPA: tissue IHC; general IHC practice). |
| Chromogen covers extracellular spaces, section edges, or nuclei and cytoplasm indiscriminately. | That distribution does not resolve the reported nuclear pattern (HPA: tissue IHC; UniProt P13010: subcellular location). Diffuse deposit can reflect background from detection reagents or staining conditions; assess a primary-antibody omission control and inspect tissue morphology (general IHC practice). |
| No nuclear signal in a breast glandular-cell or bone-marrow hematopoietic-cell section. | Both are documented High examples, so a blank result warrants a run-control check (HPA: tissue IHC). Check tissue preservation, retrieval, primary-antibody use, and detection reagents as general IHC workflow checks; the supplied sources do not establish XRCC5-specific fixation sensitivity (general IHC practice). |
💡Expected XRCC5 appearanceCall a positive result when nuclei are clearly stained in documented High cells, such as breast glandular or bone-marrow hematopoietic cells (HPA: tissue IHC); membrane-rim or widespread extracellular chromogen is suspect because XRCC5 is nuclear and lacks a transmembrane segment (UniProt P13010: subcellular location and topology; general IHC practice).
| Tissue and cell selection (HPA: tissue IHC) | HPA reports High staining in appendix endocrine cells, breast glandular cells, bone-marrow hematopoietic cells, and other listed examples; adipocytes are Low and liver cholangiocytes Not detected (HPA: tissue IHC). Score the named cell population rather than treating an entire organ as uniformly positive or negative (general IHC practice). |
| Compartment and molecular form (UniProt P13010) | Nuclear, nucleolar, and chromosome locations are annotated; no transmembrane segment, signal peptide, propeptide, or isoforms are listed (UniProt P13010: subcellular location, topology, processing, isoforms). These facts support nuclear interpretation but do not predict epitope accessibility or a particular retrieval condition (UniProt P13010; general IHC practice). |
| IHC antibody evidence (HPA: antibodies) | HPA lists IHC as Supported for HPA025813 and CAB004468; HPA064685 has no listed IHC status (HPA: antibodies). Those entries describe the named antibodies, not every XRCC5 reagent, and HPA’s tissue-level Supported rating carries medium staining–RNA consistency (HPA: antibodies and tissue IHC). |
| Endogenous detection activity (general IHC practice) | Chromogenic detection can produce signal unrelated to primary-antibody binding if endogenous activity or nonspecific reagent binding is insufficiently controlled (general IHC practice). A primary-antibody omission control helps identify detection background; a positive nuclear pattern and suitable tissue control are still needed to interpret XRCC5 staining (general IHC practice; HPA: tissue IHC). |
| IF/ICC Q: Where should XRCC5 appear? (HPA: subcellular ICC-IF) | A: Mainly in the nucleoplasm; HPA marks that location Supported (HPA: subcellular ICC-IF). UniProt also annotates nucleus, nucleolus, and chromosome (UniProt P13010: subcellular location). This is an interpretation cue for IF/ICC images, not an IF/ICC protocol or an IHC detection setting. |
| Situation | Likely cause | Next action |
|---|---|---|
| Documented High tissue has no nuclear staining (HPA: tissue IHC). | The run may have failed at tissue handling, retrieval, primary-antibody application, or chromogenic detection (general IHC practice); no XRCC5-specific fixation effect is reported in the supplied sources. | Verify the run with a documented High cell population and check each recorded IHC step and reagent control (HPA: tissue IHC; general IHC practice). Do not infer that retrieval or fixation is the XRCC5-specific cause without direct evidence. |
| Nuclei are visible but chromogen is mainly cytoplasmic or membranous. | That pattern conflicts with nuclear XRCC5 and its lack of a transmembrane segment (UniProt P13010: subcellular location and topology). Nonspecific staining is one possible explanation (general IHC practice). | Compare with a primary-antibody omission control, examine morphology, and repeat with an IHC-supported antibody if available (general IHC practice; HPA: antibodies). Score nuclear staining separately from off-compartment deposit. |
| Liver cholangiocytes stain strongly despite weak staining in a documented High control. | HPA records cholangiocytes as Not detected and the selected control as High (HPA: tissue IHC). Cross-reactivity or endogenous chromogenic activity is possible, but the pattern alone cannot identify the mechanism (general IHC practice). | Review the omission control and cell identification; compare with an independently IHC-supported XRCC5 antibody where feasible (general IHC practice; HPA: antibodies). Avoid calling every liver cell negative based on the cholangiocyte entry. |
| Brown deposit spreads across stroma, edges, or most cellular compartments. | The distribution obscures the nuclear pattern expected for XRCC5 (HPA: tissue IHC; UniProt P13010: subcellular location). Detection background or excess chromogen development can produce diffuse deposit (general IHC practice). | Inspect the primary-antibody omission control and review blocking, washing, detection, and development records (general IHC practice). Interpret only nuclei that remain distinct from background and match the tissue’s documented cell pattern (HPA: tissue IHC). |
| A low-signal adipocyte field is interpreted as a failed run. | HPA lists adipocytes as Low, so weak staining there alone is a poor failure criterion (HPA: tissue IHC). A field may also contain other cell types requiring separate identification (general IHC practice). | Use a documented High population in the same run to judge performance, then score adipocytes as their own cell population (HPA: tissue IHC; general IHC practice). Do not turn Low into an expected absence of protein. |
| An IF/ICC image shows nucleoplasmic staining, but the paraffin IHC result is unclear. | Nucleoplasm is the Supported ICC-IF location, while tissue IHC has its own Supported reliability assessment (HPA: subcellular ICC-IF and tissue IHC). The two applications provide different evidence. | Use the IF/ICC image to check compartment expectations only; resolve the IHC call with an IHC-supported antibody, tissue control, morphology, and chromogenic controls (HPA: antibodies and tissue IHC; general IHC practice). |
Experiment evidence
IHC & IF images showing XRCC5 staining
PA1641 · IHCIHC analysis of XRCC5 using anti-XRCC5 antibody (PA1641). XRCC5 was detected in paraffin-embedded section of human intestinal cancer tissue.
PA1641 · IHCIHC analysis of XRCC5 using anti-XRCC5 antibody (PA1641). XRCC5 was detected in paraffin-embedded section of human lung cancer tissue. Heat
PA1641 · IFICC analysis of XRCC5 using anti-XRCC5 antibody (PA1641). XRCC5 was detected in an immunocytochemical section of Hela cells. Enzyme antigen
PB9464 · IHCIHC analysis of KU80 using anti-KU80 antibody (PB9464). KU80 was detected in a paraffin-embedded section of human lung cancer tissue. Heat m
PB9464 · IHCIHC analysis of Ku80 using anti-Ku80 antibody (PB9464). Ku80 was detected in frozen section of human placenta tissue. The tissue section was
PB9464 · IFIF analysis of Ku80 using anti-Ku80 antibody (PB9464). Ku80 was detected in immunocytochemical section of U20S cells. Enzyme antigen retriev
M01275 · IHCImmunohistochemical analysis of paraffin-embedded human colon, using Ku80 Antibody.
HPA · Cerebral cortexHuman Protein Atlas IHC, Cerebral cortex. Source: https://www.proteinatlas.org/ENSG00000079246-XRCC5/tissue/cerebral+cortex#imid_1397764
HPA · ColonHuman Protein Atlas IHC, Colon. Source: https://www.proteinatlas.org/ENSG00000079246-XRCC5/tissue/colon#imid_1397690
HPA · LiverHuman Protein Atlas IHC, Liver. Source: https://www.proteinatlas.org/ENSG00000079246-XRCC5/tissue/liver#imid_1397675
HPA · KidneyHuman Protein Atlas IHC, Kidney. Source: https://www.proteinatlas.org/ENSG00000079246-XRCC5/tissue/kidney#imid_1397684
HPA · ICC-IF A-431Human Protein Atlas immunofluorescence, A-431, antibody HPA025813; green = XRCC5, blue = nucleus, red = microtubules.
HPA · ICC-IF A-431Human Protein Atlas immunofluorescence, A-431, antibody HPA025813; green = XRCC5, blue = nucleus, red = microtubules.
← swipe / scroll for more images →
Real IHC / IF data behind the staining-pattern expectations in this section.
Sample controls for XRCC5 IHC & IF
🧪Run bone marrow first and expect nuclear staining in hematopoietic cells (HPA: High in bone marrow hematopoietic cells; UniProt P13010: nuclear localization). Use liver cholangiocytes as the negative tissue (HPA: Not detected in liver cholangiocytes); erythrocytes on the bone marrow slide should lack nuclear staining because they have no nuclei (standard histology), but other marrow cells should not be assumed negative.
Positive control tissue: Appendix (Endocrine cells, HPA High)
Negative control tissue: Liver (HPA Not detected)
ICC-IF cell lines (HPA subcellular resource): HPA ICC-IF images show XRCC5 in A-431, U-251MG, U2OS, Rh30, SH-SY5Y, with annotated localisation: Nucleoplasm (supported) (HPA subcellular).
Technical controls: Include a no-primary, secondary-only control; a matched nonimmune rabbit IgG isotype control (selected-SKU caption: rabbit primary); and XRCC5 knockout material or a validated peptide-block control for specificity. Quench endogenous peroxidase in bone marrow before chromogenic detection to limit signal from myeloid cells (standard IHC practice).
⚠️Feasibility: No target-specific fixation window or fixation effect is reported in the supplied evidence, and the PA1641 paraffin-section caption does not state a fixative (selected-SKU tissue-IHC caption). That caption used heat retrieval in EDTA at pH 8.0, but does not establish that retrieval is required or that frozen sections or IF are easier (selected-SKU tissue-IHC caption). Bone marrow myeloid-cell peroxidase can complicate chromogenic scoring (standard IHC practice); ICC-IF images support nucleoplasmic localization in the listed cell lines, but do not establish a tissue IF protocol (HPA subcellular: Nucleoplasm, supported).
HPA tissue IHC evidence for XRCC5
Comprehensive Human Protein Atlas IHC scoring per tissue (reliability: Supported — Medium 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 |
|---|---|---|---|---|
| Appendix | Endocrine cells | High | Protein (IHC) | HPA → |
| Bone marrow | Hematopoietic cells | High | Protein (IHC) | HPA → |
| Breast | Glandular cells | High | Protein (IHC) | HPA → |
| Caudate | Glial cells | High | Protein (IHC) | HPA → |
| Cerebellum | Cells in granular layer | High | Protein (IHC) | HPA → |
Undetected expression · recommended negative controls
| Tissue | Cell type | Level | Evidence | Source |
|---|---|---|---|---|
| Liver | Cholangiocytes | Not detected | Protein (IHC) | HPA → |
Section 3
Advanced XRCC5 IHC Tips
Troubleshoot XRCC5 staining in paraffin sections by checking retrieval, nuclear localisation, controls and cell-level scoring before interpreting chromogenic signal.
What retrieval should I use if XRCC5 nuclear staining is weak?
Use heat-mediated antigen retrieval in EDTA at pH 8.0 for this IHC assay (datasheet PA1641). The selected paraffin-section example used that condition before incubation with 1 μg/ml antibody overnight at 4°C (caption PA1641). If nuclei remain weak, compare a modest range of heating durations on adjacent sections while holding antibody concentration and detection constant (standard IHC practice). Check tissue morphology after heating, because excessive retrieval can make nuclear boundaries difficult to score (standard IHC practice). A different retrieval buffer or pH is a fallback to validate with controls, since the supplied product example supports EDTA at pH 8.0 (caption PA1641).
Could fixation explain weak or uneven XRCC5 staining?
Target-specific fixation sensitivity is unknown: the selected paraffin-section caption does not report a fixative (caption PA1641). Record each specimen’s fixative and processing history, then compare sections processed together before attributing weak staining to XRCC5 biology (standard IHC practice). If fixation varies between samples, keep retrieval at EDTA pH 8.0 and detection settings constant during the comparison (datasheet PA1641; standard IHC practice). Inspect nuclear preservation and staining across the section, including its edges, because processing artefacts can produce uneven chromogenic signal (standard IHC practice). Neither nuclear localisation nor annotated modifications establish a fixation effect for this antibody (UniProt P13010).
Where should convincing XRCC5 staining appear in an IHC section?
Prioritise staining within intact nuclei: XRCC5 is annotated in the nucleus, nucleolus and on chromosomes, while the tissue profile describes ubiquitous nuclear expression (UniProt P13010; HPA tissue IHC). The supported subcellular location is mainly nucleoplasmic, so diffuse cytoplasmic DAB alone is insufficient evidence of specific staining (HPA subcellular; standard IHC practice). Compare suspected positive nuclei with nearby cells on the same section and with the negative reagent control (standard IHC practice). Use a counterstain light enough to retain visible nuclear boundaries, then assess whether DAB follows those boundaries across multiple fields (standard IHC practice). Interpret nucleolar emphasis cautiously within the broader nuclear pattern (UniProt P13010).
Could an isoform or inaccessible epitope explain discordant nuclear staining?
The supplied record lists 0 XRCC5 isoforms and a processed chain spanning residues 2–732, so an annotated isoform switch does not explain discordant IHC staining (UniProt P13010). The antibody epitope is not specified in the supplied product caption; do not assign weak staining to a particular domain or modification without epitope information (caption PA1641; UniProt P13010). XRCC5 has a VWFA domain at residues 9–231, a Ku domain at 253–452 and annotated modified residues (UniProt P13010). Compare retrieval and detection on matched sections before proposing epitope masking, and retain a nuclear-pattern control throughout (standard IHC practice; HPA subcellular).
How should I adapt the nuclear readout for multiplex IF?
Treat IF/ICC as a separate assay: the selected product example documents chromogenic IHC on a paraffin section and supplies no IF fixation condition (caption PA1641). For multiplex IF, pair XRCC5 with a validated marker of the cell type being assessed; colon endocrine cells have a high XRCC5 IHC signal in the supplied profile (HPA tissue IHC; standard IF practice). Choose fluorophores and imaging channels after checking tissue autofluorescence, particularly where background overlaps the intended XRCC5 channel (standard IF practice). XRCC5 has no transmembrane segment and is mainly nucleoplasmic, so optimise permeabilisation for nuclear access to the antibody epitope rather than assigning it a membrane side (UniProt P13010; HPA subcellular; standard IF practice).
How can I separate XRCC5 signal from chromogenic background?
The selected IHC example used 10% goat serum blocking, a biotinylated secondary, a streptavidin–biotin detection complex and DAB (caption PA1641). Run a no-primary control through the same detection steps to identify secondary or detection-system background (standard IHC practice). If diffuse brown staining persists, review blocking, endogenous peroxidase quenching and, for this biotin-based workflow, endogenous biotin controls (standard IHC practice). Compare those controls with intact nuclei in the test section, since the expected XRCC5 pattern is predominantly nuclear (HPA tissue IHC; HPA subcellular). Adjust DAB development consistently across sections so background differences do not masquerade as biological differences (standard IHC practice).
What is a defensible way to score XRCC5 IHC? ⚠ ANSWER MARKED FOR VERIFICATION
Define the cell population and score nuclear staining only, because the supplied tissue profile describes ubiquitous nuclear expression and the supported subcellular location is nucleoplasmic (HPA tissue IHC; HPA subcellular). Report the percentage of positive nuclei and, when intensity is reproducible, an H-score from intensity categories 0–3 (standard IHC practice). Normalise positive counts to the number of evaluable nuclei in the same annotated compartment, or report positive-cell density per mm² of evaluable tissue (standard IHC practice). Apply one threshold and exposure-independent chromogenic scoring rule across sections, excluding folds, necrosis and edge artefacts before comparison (standard IHC practice).
When is brown staining persuasive evidence of XRCC5 rather than artefact?
A persuasive result follows intact nuclear boundaries across evaluable cells and exceeds the matched negative-control signal (HPA tissue IHC; HPA subcellular; standard IHC practice). Check cell identity before comparing compartments: high staining is reported in colon endocrine cells, whereas liver cholangiocytes are listed as not detected in the supplied tissue profile (HPA tissue IHC). Discount isolated section-edge staining, necrotic regions and brown deposits lacking nuclear structure, which can reflect tissue or detection artefacts (standard IHC practice). If the no-primary control is brown, assess endogenous enzyme activity and the biotin-based detection workflow before assigning signal to XRCC5 (caption PA1641; standard IHC practice).
Boster reagents
Best XRCC5 / DNA repair protein Ku80 IHC Antibodies
Anti-XRCC5 antibodies have IHC images from human paraffin sections and IF images from cells and tissue (catalog captions: PA1641, PB9464, M01275); PB9464 also lists Mouse and Rat reactivity (catalog: PB9464).
Real IHC data
Anti-Ku80/XRCC5 Antibody ®
Cat # PA1641
Real IHC data
Anti-Ku80/XRCC5 Antibody ®
Cat # PB9464
Real IHC data
Anti-Ku80 XRCC5 Rabbit Monoclonal Antibody
Cat # M01275
PA1641 shows IHC in paraffin-embedded human intestinal cancer and IF in A549 cells and paraffin-embedded human intestinal cancer (catalog captions: PA1641); PB9464 shows IHC in paraffin-embedded human lung cancer and IF in U20S cells (catalog captions: PB9464). M01275 shows IHC in paraffin-embedded human colon and lists IF/ICC among its applications, although no IF image is supplied (catalog: M01275).
Which to pick: For tissue IHC, choose PA1641 for the pictured human intestinal cancer section, PB9464 for the pictured human lung cancer section, or rabbit monoclonal M01275 for the pictured human colon section; each is paraffin-embedded, and none of these captions reports the fixative (catalog IHC captions: PA1641, PB9464, M01275; catalog: M01275 clone FAE-24). For IF/ICC, PA1641 has IF images in A549 cells and human intestinal cancer tissue, while PB9464 has an IF image in U20S cells (catalog IF captions: PA1641, PB9464). For cross-species planning, PB9464 lists Human, Mouse, and Rat reactivity, although its pictured paraffin IHC uses human tissue (catalog: PB9464; catalog IHC caption: PB9464).
Each figure is that product's own IHC / IF validation image from its datasheet.
References
- UniProt Consortium. UniProt entry P13010 (XRCC5_HUMAN, DNA repair protein Ku80).
- Human Protein Atlas. XRCC5 tissue IHC expression (reliability: Supported).
- Human Protein Atlas. XRCC5 subcellular location (ICC-IF): Mainly localized to the nucleoplasm..
- Human Protein Atlas. XRCC5 antibody validation summary (3 antibodies).
- XRCC5 cooperates with p300 to promote cyclooxygenase-2 expression and tumor growth in colon cancers. PloS one 2017 — PMC5648251.
- The NRF2-dependent transcriptional axis, XRCC5/hTERT drives tumor progression and 5-Fu insensitivity in hepatocellular carcinoma. Molecular therapy oncolytics 2022 — PMC8762376.
- MSH2/BRCA1 expression as a DNA-repair signature predicting survival in early-stage lung cancer patients from the IFCT-0002 Phase 3 Trial. Oncotarget 2017 — PMC5354834.
- Overexpression of CLC-3 is regulated by XRCC5 and is a poor prognostic biomarker for gastric cancer. Journal of hematology & oncology 2018 — PMC6137920.
- PubMed PMID:2760028 — UniProt-cited evidence.
- PubMed PMID:2308937 — UniProt-cited evidence.
- PubMed PMID:14702039 — UniProt-cited evidence.
Immunohistochemistry protocol sheet for XRCC5 (DNA repair protein Ku80). Expected localisation Nuclear tissue staining (HPA tissue IHC); nucleolar and chromosomal locations are annotated (UniProt). Antigen retrieval: EDTA pH 8.0 HIER, heat-mediated (datasheet PA1641). Validated IHC antibody: PA1641 at 0.5-1μg/ml (the product's own IHC validation image is shown). Controls (HPA): positive Appendix (Endocrine cells); negative Liver. IHC-P workflow on paraffin sections; fixative unspecified. Protocol steps: 1. Sample: Paraffin-embedded human intestinal cancer tissue; fixative not specified (datasheet PA1641); 2. Fixation: Image fixative and duration unreported (datasheet PA1641); 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 PA1641); 20 min, 95–100 °C (standard); 6. Peroxidase block: 3% H2O2, 10 min , room temperature (standard); 7. Blocking: 10% goat serum (datasheet PA1641); 8. Primary antibody: Rabbit anti-XRCC5, 0.5-1μg/ml (datasheet PA1641); 9. Primary incubation: Overnight at 4 °C (datasheet PA1641). Watch for: Fixation: Keep fixation consistent across paraffin sections (standard IHC practice; not target-specific); Matched tissue-IHC evidence does not establish the fixation claim. Validate the specimen-specific method before use. (selected-SKU IHC image PA1641); Caveat: Liver cholangiocytes show no detected signal (HPA tissue IHC); Isoform / epitope: No annotated isoforms; chain spans residues 2–732 (UniProt); Regulation: Low tissue specificity (HPA tissue RNA). Evidence: UniProt P13010, HPA tissue IHC · Supported, HPA ICC-IF · Mainly localized to the nucleoplasm., Datasheet PA1641, PMC5648251, PMC8762376. QR code links to https://www.bosterbio.com/bosterbio-gene-info-cards/XRCC5/immunohistochemistry-ihc-guide.