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CRABP2 / Cellular retinoic acid-binding protein 2 · IHC design guide
Design Immunohistochemistry for CRABP2
Plan chromogenic CRABP2 IHC in paraffin sections using esophageal or vaginal squamous epithelium as a positive reference (HPA tissue IHC). Compare cytoplasmic and nuclear staining with a catalog antibody starting range of 2–5 μg/ml (datasheet A03297-3).
Evidence assembled Oct 2026 · For research use; verify linked source records and product datasheet before use
CRABP2 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 | Squamous epithelium: cytoplasm and nucleus (HPA tissue IHC) | |
| Staining pattern | Squamous epithelial cells show cytoplasmic and nuclear staining (HPA tissue IHC) | |
| Antigen retrieval | EDTA pH 8.0 HIER, heat-mediated (datasheet A03297-3) | |
| Positive control | Endometrium+4 more · see all | |
| Negative control | Adipose tissue+4 more · see all |
Important caveats
Reasons your staining may differ from the expected pattern.
| Fixation | Keep tissue fixation consistent across sections (standard IHC practice; not target-specific) | |
| Caveat | Tissue staining has low consistency with RNA expression (HPA tissue IHC) | |
| Regulation | Ligand binding drives nuclear import (UniProt) | |
| Isoform / epitope | No isoforms annotated; one chain spans residues 1–138 (UniProt) |
Section 1
Recommended CRABP2 IHC & IF Protocols
The catalog antibody has an IHC-P protocol (datasheet A03297-3). Four published CRABP2 IHC protocols provide additional FFPE examples (PMC12486367; PMC8477672; PMC6389245; PMC10225231).
| Sample | Paraffin-embedded human laryngeal squamous cell carcinoma tissue; fixative not specified (datasheet A03297-3) |
| Fixation | Image fixative and duration unreported (datasheet A03297-3); 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 A03297-3); 20 min, 95–100 °C (standard) |
| Peroxidase block | 3% H2O2, 10 min, room temperature (standard) |
| Blocking | 10% goat serum (datasheet A03297-3) |
| Primary antibody | Rabbit anti-CRABP2, 2-5 μg/ml (datasheet A03297-3) |
| Primary incubation | Overnight at 4 °C (datasheet A03297-3) |
| Detection | HRP-conjugated secondary, DAB chromogen (datasheet A03297-3) |
| Counterstain | Hematoxylin, blue, dehydrate and mount (standard) |
| Expected result | CRABP2-positive staining in macrophages of endometrium (HPA tissue IHC: High). HPA tissue profile: Cytoplasmic and nuclear expression in squamous epithelia. Additional cytoplasmic expression in salivary and breast glands. No signal in the no-primary control. |
💡Decision noteStart with heat-mediated EDTA pH 8.0 retrieval for the catalog antibody (datasheet A03297-3); a published TMA protocol uses EDTA pH 9.0 (PMC8477672).
Section 2
What Is the Expected CRABP2 Staining Pattern?
CRABP2 should appear in the cytoplasm and nuclei of squamous epithelial cells, especially in esophagus and vagina (HPA: tissue IHC). Cytoplasmic staining is also reported in salivary and breast glands (HPA: tissue IHC). A soluble protein without a transmembrane segment, CRABP2 can move into the nucleus after ligand binding (UniProt P29373: topology and localization). HPA rates its tissue IHC reliability Supported while reporting low consistency with RNA expression (HPA: reliability).
| Cytoplasmic and nuclear staining in esophageal or vaginal squamous epithelial cells (HPA: High in both). | This matches the reported tissue pattern (HPA: tissue IHC). Score the stained cells and compartments together; nuclear staining is plausible because ligand binding can promote CRABP2 nuclear transport (UniProt P29373: localization). |
| Predominantly membranous staining, with little cytoplasmic or nuclear signal (HPA: expected tissue pattern). | Question antibody specificity or staining artefact. CRABP2 has no transmembrane segment (UniProt P29373: topology), and HPA reports cytoplasmic and nuclear staining rather than a membrane pattern (HPA: tissue IHC). |
| Strong staining in cells reported as undetected, such as adipocytes in adipose tissue (HPA: Not detected). | Consider cross-reactivity or endogenous detection activity (general IHC practice). Identify the stained cell type before judging the whole section: an unexpected positive cell does not establish a new CRABP2 tissue pattern (HPA: tissue IHC). |
| Diffuse color across tissue, including spaces without cells (general IHC practice). | This is background rather than convincing cellular localization (general IHC practice). Compare with a no-primary control and reassess blocking, washes, and detection conditions before scoring CRABP2 (general IHC practice). |
| No staining in esophageal squamous epithelium alongside the test section (HPA: High in esophagus). | Treat the run as inconclusive before interpreting a test section as negative. Check the control tissue, antibody dilution, retrieval, and detection steps (general IHC practice); HPA's High rating is an observed pattern, not a guaranteed result (HPA: tissue IHC). |
💡Expected CRABP2 appearanceCall positive when squamous epithelial cells show clear cytoplasmic and nuclear staining, especially in esophagus or vagina (HPA: High); isolated membrane staining or color outside cells is suspicious (UniProt P29373: topology; general IHC practice).
| Compartment and ligand state (UniProt P29373: localization). | UniProt lists cytoplasm, endoplasmic reticulum, and nucleus and describes ligand-dependent nuclear transport (UniProt P29373: localization). Nuclear signal can vary; routine chromogenic IHC cannot by itself prove ligand exposure or resolve endoplasmic reticulum (general IHC practice). |
| Tissue and cell context (HPA: tissue IHC). | Esophageal and vaginal squamous epithelial cells are High; cervical and oral squamous epithelial cells are Medium (HPA: tissue IHC). Compare like cell types when scoring, since a tissue label alone can conceal which cells stain (general IHC practice). |
| Reference negative cells (HPA: tissue IHC). | Adipocytes and adrenal glandular cells are listed as Not detected (HPA: tissue IHC). Use these as comparison patterns, while recognizing that HPA's Supported rating includes low consistency between antibody staining and RNA data (HPA: reliability). |
| Antibody evidence (HPA: antibody validation). | HPA004135 and CAB080413 each have Supported IHC status; HPA004135 also has Supported ICC status (HPA: antibody validation). These ratings support comparison with reported patterns but do not establish that every antibody or staining run behaves identically (general IHC practice). |
| IF/ICC Q&A: Where should fluorescence appear? (HPA: subcellular ICC-IF). | Expect nucleoplasm and cytosol, both supported in HPA ICC-IF images (HPA: subcellular ICC-IF). This answers the localization question for IF/ICC; the paraffin-section chromogenic IHC pattern remains the primary interpretation here (HPA: tissue IHC). |
| Topology and processing (UniProt P29373: sequence annotation). | CRABP2 is a 138-residue chain with no annotated signal peptide, propeptide, transmembrane segment, or glycosylation site (UniProt P29373: sequence annotation). Those facts provide no target-specific basis for predicting a fixation or retrieval effect (UniProt P29373: sequence annotation). |
| Situation | Likely cause | Next action |
|---|---|---|
| Known-positive squamous epithelium is blank (HPA: High in esophagus and vagina). | The staining run or control may have failed; absence of signal alone cannot distinguish technical failure from low antigen detection (general IHC practice). | Confirm tissue identity and preservation, then review retrieval, antibody dilution, incubation, and chromogenic detection using the established laboratory controls (general IHC practice). |
| Nuclei stain, but cytoplasm is weak (HPA: tissue IHC pattern). | CRABP2 can enter nuclei after ligand binding (UniProt P29373: localization); differing compartment intensity alone does not prove a faulty stain. | Check whether signal remains within the expected squamous epithelial cells and compare a matched positive control before assigning an abnormal pattern (HPA: tissue IHC; general IHC practice). |
| Only cell borders appear positive (HPA: expected cytoplasmic and nuclear pattern). | A membrane-only pattern conflicts with the reported localization and lack of a transmembrane segment (HPA: tissue IHC; UniProt P29373: topology). | Inspect a no-primary control and repeat with an independently supported IHC antibody if available (general IHC practice; HPA: HPA004135 and CAB080413 Supported). |
| Unexpected cells stain strongly in a reference-negative tissue (HPA: Not detected examples). | Cross-reactivity or endogenous detection activity is possible (general IHC practice); HPA's negative calls apply to specified cell types (HPA: tissue IHC). | Identify the positive cells, compare a no-primary control, and review endogenous activity blocking appropriate to the detection chemistry (general IHC practice). |
| Diffuse chromogen obscures epithelial cells (general IHC practice). | Excess background may reflect insufficient blocking or washing, or overly strong detection conditions (general IHC practice). | Compare the no-primary control, improve blocking and washes as indicated, and adjust detection conditions before rescoring cellular localization (general IHC practice). |
| A sample disagrees with HPA's tissue pattern (HPA: tissue IHC). | HPA rates the IHC evidence Supported but notes low consistency with RNA expression (HPA: reliability); a single discordant section is inconclusive. | Verify cell identity and staining controls, then document compartment and cell-specific intensity. Treat an unresolved result as uncertain rather than extending the reference pattern (general IHC practice). |
Experiment evidence
IHC & IF images showing CRABP2 staining
A03297-3 · IHCIHC analysis of CRABP2 using anti-CRABP2 antibody (A03297-3). CRABP2 was detected in a paraffin-embedded section of human laryngeal squamous
A30602 · IHCImmunohistochemical analysis of paraffin-embedded human colon cancer. 1, Tris-EDTA,pH9.0 was used for antigen retrieval. 2 Antibody was dilu
HPA · Cerebral cortexHuman Protein Atlas IHC, Cerebral cortex. Source: https://www.proteinatlas.org/ENSG00000143320-CRABP2/tissue/cerebral+cortex#imid_1471064
HPA · EsophagusHuman Protein Atlas IHC, Esophagus. Source: https://www.proteinatlas.org/ENSG00000143320-CRABP2/tissue/esophagus#imid_1471028
HPA · ColonHuman Protein Atlas IHC, Colon. Source: https://www.proteinatlas.org/ENSG00000143320-CRABP2/tissue/colon#imid_1470990
HPA · LiverHuman Protein Atlas IHC, Liver. Source: https://www.proteinatlas.org/ENSG00000143320-CRABP2/tissue/liver#imid_1470999
HPA · ICC-IF A-431Human Protein Atlas immunofluorescence, A-431, antibody HPA004135; green = CRABP2, blue = nucleus, red = microtubules.
HPA · ICC-IF A-431Human Protein Atlas immunofluorescence, A-431, antibody HPA004135; green = CRABP2, blue = nucleus, red = microtubules.
← swipe / scroll for more images →
Real IHC / IF data behind the staining-pattern expectations in this section.
Sample controls for CRABP2 IHC & IF
🧪Run esophagus first: its squamous epithelial cells should stain (HPA: High in esophageal squamous epithelial cells). Run adipose tissue as a negative comparator (HPA: Not detected in adipocytes); on the esophagus slide, use adjacent stromal cells lacking specific DAB staining as candidate internal negative cells, while verifying their identity and staining pattern.
Positive control tissue: Endometrium (Macrophages, HPA High)
Negative control tissue: Adipose tissue (HPA Not detected)
ICC-IF cell lines (HPA subcellular resource): HPA ICC-IF images show CRABP2 in A-431, U-251MG, U2OS, with annotated localisation: Nucleoplasm (supported), Cytosol (supported) (HPA subcellular).
Technical controls: Include a no-primary, secondary-only control and a rabbit isotype control matched to the primary antibody’s clonality and concentration where applicable (caption: rabbit anti-CRABP2 antibody). Use CRABP2 knockout material or a validated peptide-block control as a biological negative, and quench endogenous peroxidase before DAB detection in the esophagus section (caption: HRP/DAB detection; standard IHC practice).
⚠️Feasibility: A target-specific fixation window and fixation effect are unreported, and the selected A03297-3 tissue-IHC caption does not state the fixative (caption: fixative not stated). Paraffin-section IHC has a documented starting condition of heat retrieval in EDTA at pH 8.0; the evidence does not establish whether retrieval is required or whether frozen sections or IF are easier (caption: EDTA heat retrieval; HPA: ICC-IF images available). In esophagus, inspect superficial keratin and section edges for nonspecific DAB deposition before scoring squamous epithelial staining (HPA: High in esophageal squamous epithelial cells; standard IHC practice).
HPA tissue IHC evidence for CRABP2
Comprehensive Human Protein Atlas IHC scoring per tissue (reliability: Supported — Low 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 |
|---|---|---|---|---|
| Endometrium | Macrophages | High | Protein (IHC) | HPA → |
| Esophagus | Squamous epithelial cells | High | Protein (IHC) | HPA → |
| Skin | Eccrine glands | High | Protein (IHC) | HPA → |
| Vagina | Squamous epithelial cells | High | Protein (IHC) | HPA → |
| Breast | 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 → |
| Bronchus | Respiratory epithelial cells | Not detected | Protein (IHC) | HPA → |
Section 3
Advanced CRABP2 IHC Tips
Troubleshoot CRABP2 staining by checking retrieval, controls, and cellular compartment before comparing chromogenic IHC scores (UniProt P29373; HPA tissue IHC).
What retrieval should I start with for CRABP2 in paraffin sections?
Start with heat-mediated retrieval in EDTA at pH 8.0 for the catalog antibody (datasheet A03297-3). Run a known staining control alongside the test section, keeping heating and cooling conditions consistent between runs (standard IHC practice). The illustrated paraffin-section workflow used 2 μg/ml primary antibody overnight at 4°C, so reproduce that concentration before changing retrieval conditions (datasheet A03297-3). If staining is weak, vary heating duration on adjacent sections while holding antibody concentration and detection constant (standard IHC practice). Compare tissue preservation as well as signal, because excessive heat can damage section morphology (standard IHC practice).
Could fixation explain weak CRABP2 staining in my paraffin sections?
Target-specific fixation sensitivity is unknown: the catalog antibody’s paraffin-section caption does not state a fixative (datasheet A03297-3). Record the fixative and fixation duration for each specimen, then compare sections processed and stained together (standard IHC practice). Keep the documented EDTA retrieval at pH 8.0 and primary concentration at 2 μg/ml constant while assessing fixation differences (datasheet A03297-3). Evaluate both staining and morphology against a control section from the same processing batch (standard IHC practice). Neither the reported tissue staining pattern nor the absence of a transmembrane segment establishes how this target responds to fixation (HPA tissue IHC; UniProt P29373 topology).
Should CRABP2 stain nuclei, cytoplasm, or both?
Expect cytoplasmic and nuclear staining in squamous epithelia, with additional cytoplasmic staining reported in salivary and breast glands (HPA tissue IHC). Nucleoplasmic and cytosolic localisation is also supported by cell imaging, while ligand binding can promote nuclear transport (HPA subcellular; UniProt P29373). Score nuclear and cytoplasmic staining separately in the intended cell population rather than treating any brown signal as equivalent (standard IHC practice). Check the pattern against a positive control, such as esophageal squamous epithelial cells, and a no-primary control (HPA: High in esophageal squamous epithelial cells; standard IHC practice). Interpret discordant patterns cautiously because tissue IHC has low consistency with RNA expression (HPA tissue IHC: Supported reliability).
Could an isoform or inaccessible epitope account for inconsistent staining?
The supplied protein record lists a 138-amino-acid chain and no annotated isoforms, so isoform choice does not explain staining differences on this evidence (UniProt P29373). It also lists no transmembrane segment or annotated glycosylation sites, but neither observation identifies this antibody’s epitope (UniProt P29373). Check the antibody documentation for its immunogen or epitope before attributing a negative section to epitope loss (standard IHC practice). Compare adjacent sections under the documented EDTA pH 8.0 retrieval while changing only one staining variable at a time (datasheet A03297-3; standard IHC practice). Preserve a positive tissue control in each comparison to distinguish section-level failure from specimen variation (standard IHC practice).
How should I adapt CRABP2 staining for multiplex immunofluorescence?
Treat IF/ICC as a separate assay: the supplied antibody caption documents chromogenic staining of a paraffin section, while HPA reports CRABP2 nucleoplasmic and cytosolic imaging (datasheet A03297-3; HPA subcellular). Multiplex CRABP2 with a validated marker for the expected cell population, such as squamous epithelial cells in esophagus, and assess channel overlap within individual cells (HPA: High in esophageal squamous epithelial cells; standard IF practice). Choose spectrally separated fluorophores after checking tissue autofluorescence in unstained controls; a far-red channel may improve contrast if that background is lower (standard IF practice). After fixation, optimise permeabilisation to expose cytosolic and nuclear epitopes without disrupting morphology (HPA subcellular; standard IF practice). Confirm the antibody’s IF suitability independently before interpreting colocalisation (standard IF practice).
How can I reduce diffuse brown staining without losing CRABP2 signal?
Start by comparing stained sections with no-primary controls and inspecting whether brown deposit follows tissue structures or appears broadly across the slide (standard IHC practice). The illustrated workflow blocked with 10% goat serum, used 2 μg/ml primary antibody overnight at 4°C, and developed with DAB (datasheet A03297-3). If background persists, optimise primary concentration and wash stringency while keeping retrieval fixed at EDTA pH 8.0 (datasheet A03297-3; standard IHC practice). Include a peroxidase block to assess endogenous enzyme contribution; that block is a general chromogenic workflow step, not documented target-specific evidence (standard IHC practice). Judge improvements against retained signal in a positive tissue control (standard IHC practice).
What is a defensible way to quantify CRABP2 IHC across samples? ⚠ ANSWER MARKED FOR VERIFICATION
Define the cell population and anatomical region before scoring, then use the same imaging and DAB analysis settings for every section (standard IHC practice). Report percentage of positive cells and staining intensity separately for nuclei and cytoplasm, reflecting both documented compartments (HPA tissue IHC; UniProt P29373). If using an H-score, multiply the percentage at each intensity level by its 0–3 grade and sum to a 0–300 score (standard IHC practice). Normalise cell counts to the number of eligible cells, or positive-cell density to the measured area in mm², rather than to total slide area (standard IHC practice). Include matched negative controls when setting the positivity threshold (standard IHC practice).
How do I distinguish true CRABP2 staining from artefact?
Give greatest weight to reproducible cytoplasmic or nuclear staining in morphologically intact cells, because both compartments are documented for CRABP2 (HPA tissue IHC; UniProt P29373). Esophageal squamous epithelial cells provide a reported high-expression reference, whereas adipocytes are reported as not detected (HPA tissue IHC). Examine section edges and necrotic areas separately, and reject deposit reproduced in a no-primary control or attributable to endogenous peroxidase (standard IHC practice). A brown signal confined to an unexpected compartment or cell population needs independent confirmation before assignment to CRABP2 (HPA tissue IHC; standard IHC practice). Avoid inferring protein abundance directly from RNA because the tissue IHC profile has low staining–RNA consistency (HPA tissue IHC: Supported reliability).
Boster reagents
Best CRABP2 / Cellular retinoic acid-binding protein 2 IHC Antibodies
Two antibodies have human paraffin-section IHC figures (A03297-3 and A30602 captions); A30602 also lists IF/ICC and reactivity with human, mouse and rat (A30602 catalog).
Real IHC data
Anti-CRABP2 Antibody ®
Cat # A03297-3
Real IHC data
Anti-CRABP2 Antibody
Cat # A30602
A03297-3 has an IHC figure from human laryngeal squamous cell carcinoma in a paraffin section (A03297-3 caption). A30602 has an IHC figure from human colon cancer in a paraffin section and lists IF/ICC applications (A30602 caption; A30602 catalog).
Which to pick: For human paraffin-section IHC, A03297-3 provides an EDTA pH 8 retrieval and 2 μg/ml overnight incubation example (A03297-3 caption). Choose A30602 for IF/ICC or work involving human, mouse and rat because those applications and species are listed (A30602 catalog); its human paraffin-section IHC example uses Tris-EDTA pH 9 and 1:200 overnight incubation (A30602 caption). The fixative is unreported in both IHC captions (A03297-3 and A30602 captions).
Each figure is that product's own IHC / IF validation image from its datasheet.
References
- UniProt Consortium. UniProt entry P29373 (RABP2_HUMAN, Cellular retinoic acid-binding protein 2).
- Human Protein Atlas. CRABP2 tissue IHC expression (reliability: Supported).
- Human Protein Atlas. CRABP2 subcellular location (ICC-IF): Localized to the nucleoplasm and cytosol..
- Human Protein Atlas. CRABP2 antibody validation summary (2 antibodies).
- Identification of key molecules in micropapillary progression of lung adenocarcinoma: A comprehensive gene expression analysis study using the spatial gene expression solution methodology. Oncology letters 2025 — PMC12486367.
- Expression and function analysis of CRABP2 and FABP5, and their ratio in esophageal squamous cell carcinoma. Open medicine (Warsaw, Poland) 2021 — PMC8477672.
- Tissue expression of retinoic acid receptor alpha and CRABP2 in metastatic nephroblastomas. Diagnostic pathology 2018 — PMC6389245.
- In-depth proteomics reveals the characteristic developmental profiles of early lung adenocarcinoma with epidermal growth factor receptor mutation. Cancer medicine 2023 — PMC10225231.
- PubMed PMID:1654334 — UniProt-cited evidence.
- PubMed PMID:1309505 — UniProt-cited evidence.
- PubMed PMID:1334086 — UniProt-cited evidence.
Immunohistochemistry protocol sheet for CRABP2 (Cellular retinoic acid-binding protein 2). Expected localisation Squamous epithelium: cytoplasm and nucleus (HPA tissue IHC). Antigen retrieval: EDTA pH 8.0 HIER, heat-mediated (datasheet A03297-3). Validated IHC antibody: A03297-3 at 2-5 μg/ml (the product's own IHC validation image is shown). Controls (HPA): positive Endometrium (Macrophages); negative Adipose tissue. IHC-P workflow on paraffin sections; fixative unspecified. Protocol steps: 1. Sample: Paraffin-embedded human laryngeal squamous cell carcinoma tissue; fixative not specified (datasheet A03297-3); 2. Fixation: Image fixative and duration unreported (datasheet A03297-3); 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 A03297-3); 20 min, 95–100 °C (standard); 6. Peroxidase block: 3% H2O2, 10 min , room temperature (standard); 7. Blocking: 10% goat serum (datasheet A03297-3); 8. Primary antibody: Rabbit anti-CRABP2, 2-5 μg/ml (datasheet A03297-3); 9. Primary incubation: Overnight at 4 °C (datasheet A03297-3). Watch for: Fixation: Keep tissue fixation consistent across sections (standard IHC practice; not target-specific); Caveat: Tissue staining has low consistency with RNA expression (HPA tissue IHC); Isoform / epitope: No isoforms annotated; one chain spans residues 1–138 (UniProt); Regulation: Ligand binding drives nuclear import (UniProt). Evidence: UniProt P29373, HPA tissue IHC · Supported, HPA ICC-IF · nucleoplasm and cytosol., Datasheet A03297-3, PMC12486367, PMC8477672. QR code links to https://www.bosterbio.com/bosterbio-gene-info-cards/CRABP2/immunohistochemistry-ihc-guide.