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CRABP2 / Cellular retinoic acid-binding protein 2 · IHC design guide
Design Immunohistochemistry for CRABP2
Plan CRABP2 paraffin IHC around cytoplasmic and nuclear staining in squamous epithelia (HPA tissue IHC). Compare cell type and compartment across controls (standard IHC practice), starting with the catalog antibody’s 2–5 μg/ml IHC range (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 | Cytoplasmic and nuclear tissue staining (HPA tissue IHC) | |
| Staining pattern | Squamous epithelial cytoplasm and nuclei; glandular cytoplasm (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 fixation consistent across paraffin sections. (standard IHC practice; not target-specific) | |
| Caveat | Antibody staining and RNA show low consistency (HPA tissue IHC) | |
| Regulation | Expression regulation not annotated (UniProt) | |
| Isoform / epitope | No isoforms; one 1–138 chain with no extracellular segment (UniProt) |
Section 1
Recommended CRABP2 IHC & IF Protocols
Compare the catalog antibody’s IHC-P retrieval protocol (datasheet A03297-3) with four published CRABP2 IHC protocols (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 at pH 8.0 (datasheet A03297-3); EDTA at pH 9.0 is a published alternative (PMC8477672).
Section 2
What Is the Expected CRABP2 Staining Pattern?
CRABP2 is a 138-aa protein with no transmembrane segment (UniProt P29373 topology). Expect cytoplasmic and nuclear staining in squamous epithelia, with additional cytoplasmic staining in salivary and breast glands (HPA tissue IHC). HPA rates the tissue pattern Supported but reports low consistency between antibody staining and RNA expression; interpret an unexpected result alongside tissue controls (HPA tissue IHC).
| Squamous epithelial cells show cytoplasmic and nuclear chromogen, especially in esophagus or vagina. | This fits the reported compartment pattern and High staining in those cells (HPA tissue IHC). Score the epithelial cells themselves; surrounding tissue does not establish a positive result for the intended cell population (general IHC practice). |
| Staining is confined to cell borders or an extracellular deposit, with no convincing intracellular signal. | A border-only or extracellular pattern does not match the reported cytoplasmic and nuclear distribution (HPA tissue IHC; UniProt P29373 topology). Treat it as possible nonspecific staining and compare it with a known-positive section before interpreting CRABP2 expression (general IHC practice). |
| Strong staining appears mainly in a cell population reported as undetected, such as adipocytes. | HPA reports adipocytes as Not detected, while its positive patterns are cell-type specific (HPA tissue IHC). Consider cross-reactivity or endogenous detection activity, especially if the same deposit appears on a section run without primary antibody (general IHC practice). |
| Pale, diffuse chromogen covers cells and spaces without clear intracellular boundaries. | This cannot be scored confidently as CRABP2 because the expected pattern is cellular and compartmental (HPA tissue IHC). Assess the no-primary control and whether the background persists across unrelated tissue regions; those comparisons help distinguish assay background from interpretable staining (general IHC practice). |
| Esophageal or vaginal squamous epithelium shows no signal. | Both are reported High in squamous epithelial cells, so absence of staining warrants an assay check (HPA tissue IHC). HPA also reports low agreement between staining and RNA data; one negative section alone cannot establish that CRABP2 is absent (HPA tissue IHC). |
💡Expected CRABP2 appearanceCall a positive when squamous epithelial cells show clear cytoplasmic and nuclear staining, with High staining expected in esophagus or vagina (HPA tissue IHC); isolated border, extracellular, or diffuse noncellular chromogen is an atypical pattern to investigate (HPA tissue IHC; general IHC practice).
| Ligand-dependent localization (UniProt P29373 function and subcellular annotation). | CRABP2 transports retinoic acid to the nucleus; ligand binding exposes a nuclear localization motif and promotes nuclear transport (UniProt P29373). Thus, nuclear signal can be biologically plausible alongside cytoplasmic signal, although this record supplies no treatment-specific staining prediction. |
| Topology and processing (UniProt P29373 topology and processing). | The annotated chain spans residues 1–138, with no signal peptide, propeptide, or transmembrane segment (UniProt P29373). An exclusively membranous or secreted-looking pattern therefore lacks support from this record; these annotations do not predict antigen-retrieval conditions or fixation sensitivity. |
| Strength of tissue evidence (HPA tissue IHC; HPA antibody validation). | HPA lists the overall tissue result as Supported and both listed antibodies as IHC Supported, while noting low staining-to-RNA consistency (HPA tissue IHC; HPA antibody validation). Use reported cell patterns as guides, with controls when a result conflicts; no IHC Enhanced designation is supplied. |
| IF/ICC Q: Where should signal appear? | A: HPA reports supported nucleoplasm and cytosol localization in ICC-IF and lists images from A-431, U-251MG, and U2OS (HPA subcellular). This answers localization only; the IF/ICC workflow belongs to its own guide. |
| Situation | Likely cause | Next action |
|---|---|---|
| No staining in an esophageal or vaginal positive control. | These squamous epithelial cells are reported High, making an assay issue plausible, although a single section does not identify its cause (HPA tissue IHC; general IHC practice). | Check that the positive-control tissue is present and evaluable, then review primary-antibody use, antigen retrieval, detection reagents, and counterstain against the validated IHC workflow (general IHC practice). Do not infer CRABP2-specific retrieval or fixation sensitivity from this record. |
| Only nuclei stain in squamous epithelium. | Nuclear localization is biologically plausible after ligand binding, but HPA describes both nuclear and cytoplasmic expression in squamous epithelia (UniProt P29373; HPA tissue IHC). | Confirm that nuclear chromogen is distinct from the counterstain and assess cytoplasmic signal on the same slide (general IHC practice). Record the nuclear-predominant observation without inferring ligand exposure from staining alone (UniProt P29373). |
| Breast or salivary gland staining is faint beside a strong squamous control. | HPA reports Medium breast glandular staining and Low salivary glandular staining; its profile describes additional cytoplasmic gland staining (HPA tissue IHC). | Evaluate the glandular cells and cytoplasmic compartment separately from the squamous control (HPA tissue IHC; general IHC practice). Avoid calling a weak gland result a failed run when the positive control performs and the gland pattern is interpretable. |
| A supposedly negative region develops broad brown staining. | Adipocytes and several other specified cell populations are Not detected by HPA; broad color there may reflect nonspecific binding or endogenous detection activity (HPA tissue IHC; general IHC practice). | Compare a section run without primary antibody and inspect whether color follows cells or spreads across tissue (general IHC practice). If using enzyme detection, review the applicable endogenous-activity blocking step before scoring the region. |
| Two IHC antibodies give different cell patterns. | HPA marks both listed antibodies IHC Supported but reports low consistency between tissue staining and RNA expression; this record does not resolve every discordant cell-level result (HPA antibody validation; HPA tissue IHC). | Compare matched sections using the same scoring criteria and known-positive cell types, then document which antibody produced each pattern (general IHC practice; HPA tissue IHC). Treat discordant staining outside reported cells as unresolved rather than assigning expression from one slide. |
| A no-primary control shows the same diffuse deposit as the test section. | A deposit that persists without primary antibody points to detection-related background rather than antibody-dependent CRABP2 signal (general IHC practice). | Review blocking, washing, and chromogen development for the chosen IHC detection system, then reassess the test alongside its control (general IHC practice). Score only distinct cellular staining in a supported compartment and cell type (HPA tissue IHC; 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 strongly (HPA: High in squamous epithelial cells); use adjacent stromal cells as candidate internal negatives and expect little or no staining only after confirming their CRABP2-negative status. Run bronchus as the negative tissue and assess its respiratory epithelial cells (HPA: Not detected in respiratory epithelial cells).
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 no-primary (secondary-only) and concentration-matched nonimmune rabbit IgG isotype controls, plus CRABP2-knockout material as a biological negative if available (selected-SKU caption: rabbit primary; standard IHC practice). Quench endogenous peroxidase before chromogenic detection and check for background in the esophagus section (selected-SKU caption: HRP/DAB detection; standard IHC practice).
⚠️Feasibility: A target-specific fixation window or fixation effect is unreported, and the selected-SKU paraffin-section caption does not state the fixative (selected-SKU caption: fixative unreported). Heat retrieval in EDTA at pH 8.0 was used for the catalog antibody, but the evidence does not establish that retrieval is required under every condition (selected-SKU caption: EDTA retrieval, pH 8.0). Frozen sections and IF cannot be judged easier from the supplied evidence; in esophagus, distinguish squamous epithelial staining from background in adjacent tissue when scoring (HPA: High in esophageal squamous epithelial cells; selected-SKU caption: paraffin-section IHC).
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 in paraffin sections by checking retrieval, cell identity, and cytoplasmic versus nuclear signal before interpreting intensity.
What retrieval should I try first if CRABP2 staining is weak?
Start with heat-mediated antigen retrieval in EDTA buffer at pH 8.0 (datasheet A03297-3). The catalog antibody produced CRABP2 staining in a paraffin section of human laryngeal squamous cell carcinoma using that retrieval, followed by 2 μg/ml primary antibody overnight at 4°C (datasheet A03297-3). If staining is weak, first check heating consistency, section adhesion, reagent freshness, and a positive squamous epithelial control before changing the buffer (HPA: high in esophageal squamous epithelial cells). Record retrieval temperature and duration for every run, then compare any adjusted condition on adjacent sections with identical detection and counterstaining.
Could fixation explain weak or uneven CRABP2 staining?
Target-specific fixation sensitivity is unknown: the selected tissue-IHC caption identifies a paraffin section but does not state its fixative (datasheet A03297-3). Record the fixative, fixation duration, tissue thickness, and time before fixation for each specimen, since inconsistent processing can produce uneven chromogenic staining (standard IHC practice). Compare similarly processed sections before attributing a weak result to CRABP2 biology, and keep retrieval and antibody incubation constant during that comparison (datasheet A03297-3: EDTA pH 8.0; 2 μg/ml overnight at 4°C). Do not infer fixation tolerance from the reported tissue distribution or protein topology (HPA: tissue IHC profile; UniProt P29373: no transmembrane segment).
How should I assess cytoplasmic and nuclear CRABP2 staining?
Score cytoplasmic and nuclear staining separately in the relevant cells: both compartments are plausible for CRABP2 (UniProt P29373: cytoplasm and nucleus; HPA: cytoplasmic and nuclear staining in squamous epithelia). Ligand binding can expose a nuclear localization motif and promote nuclear transport, so nuclear staining alone does not establish a change in total protein abundance (UniProt P29373: ligand-dependent transport). Compare compartment patterns in intact, similarly processed cells and use the counterstain to identify nuclei rather than calling perinuclear pigment nuclear signal (standard IHC practice). The HPA subcellular assessment also supports nucleoplasm and cytosol localization, which can guide review of ambiguous fields (HPA: supported nucleoplasm and cytosol).
Could an isoform or hidden epitope explain discordant CRABP2 staining?
No alternative isoforms are annotated, and the recorded CRABP2 chain spans residues 1–138 (UniProt P29373: isoforms 0; chain 1–138). The record lists no signal peptide, transmembrane segment, glycosylation sites, or modified residues, but it does not identify the catalog antibody's epitope (UniProt P29373: processing, topology, and annotations; datasheet A03297-3: epitope unspecified). Do not assign weak staining to a particular isoform or masked residue without independent epitope evidence. Instead, compare the established EDTA pH 8.0 retrieval with carefully documented adjustments on adjacent sections, while holding primary incubation and detection constant (datasheet A03297-3: retrieval and incubation; standard IHC practice).
How can I check an IHC pattern with multiplex IF?
Use IF as an orthogonal check of the chromogenic pattern, with a marker that identifies the squamous epithelial cells expected to express CRABP2 (HPA: high in esophageal and vaginal squamous epithelial cells). Choose spectrally separated fluorophores and favor a far-red channel for a weak target when the tissue has strong short-wavelength autofluorescence; include single-color and unstained controls (standard IF practice). CRABP2 lacks a transmembrane segment and is reported in cytosol and nucleoplasm, so permeabilise cells to assess intracellular staining while checking that nuclear boundaries remain clear (UniProt P29373: topology; HPA: supported locations). Validate IF fixation and antibody conditions independently, because the selected caption documents paraffin-section chromogenic IHC and leaves the fixative unstated (datasheet A03297-3).
What should I check when DAB background obscures CRABP2?
Run a no-primary control through the same secondary antibody and DAB steps to locate detection-related background, and block endogenous peroxidase before chromogen development (standard chromogenic IHC practice). The demonstrated workflow used 10% goat serum blocking, a peroxidase-conjugated secondary antibody, and DAB detection (datasheet A03297-3). If diffuse staining persists, compare a primary-antibody titration around the documented 2 μg/ml condition while keeping retrieval and development time fixed (datasheet A03297-3: primary concentration; standard IHC practice). Judge background against cell morphology and an appropriate control section, because CRABP2 can occur in both cytoplasm and nucleus (HPA: squamous epithelial profile; UniProt P29373: localization).
How should I quantify CRABP2 across paraffin sections? ⚠ ANSWER MARKED FOR VERIFICATION
Define the cell population and tissue area before scoring; for squamous tissue, distinguish epithelial cells from stromal and inflammatory cells (HPA: squamous epithelial staining; high staining in endometrial macrophages). Report the percentage of positive cells and a compartment-specific intensity score, or calculate an H-score from intensity categories 0–3 and their cell percentages, yielding 0–300 (standard IHC scoring practice). Normalize cell counts or positive-cell density to the number of eligible cells or analyzed tissue area in mm², respectively, and apply one threshold across the comparison (standard IHC practice). Record cytoplasmic and nuclear results separately, along with retrieval and batch details, because CRABP2 occupies both compartments (UniProt P29373: localization).
How can I distinguish genuine CRABP2 staining from artefact?
A credible pattern has staining in intact cells with interpretable cytoplasmic or nuclear boundaries, particularly within squamous epithelium (HPA: cytoplasmic and nuclear squamous epithelial expression; UniProt P29373: localization). Check the precise cell type before calling a section negative or positive: HPA reports high staining in esophageal squamous epithelial cells and endometrial macrophages, but no detected staining in adipocytes (HPA: tissue IHC). Treat signal confined to section edges, necrotic areas, or no-primary controls as suspect, and assess endogenous peroxidase when DAB deposits persist (standard chromogenic IHC practice). Interpret differences cautiously because HPA rates the tissue staining as supported while reporting low consistency with RNA expression (HPA: reliability description).
Boster reagents
Best CRABP2 / Cellular retinoic acid-binding protein 2 IHC Antibodies
Two catalog antibodies have real IHC images from human paraffin sections (catalog IHC captions). A30602 also lists IF/ICC and human, mouse and rat reactivity (catalog applications; catalog reactivity).
Real IHC data
Anti-CRABP2 Antibody ®
Cat # A03297-3
Real IHC data
Anti-CRABP2 Antibody
Cat # A30602
A03297-3 was demonstrated by IHC on a paraffin section of human laryngeal squamous cell carcinoma (A03297-3 IHC caption). A30602 was demonstrated by IHC on a paraffin section of human colon cancer (A30602 IHC caption).
Which to pick: For paraffin-section IHC, choose A03297-3 for the laryngeal carcinoma example or A30602 for the colon cancer example; the fixative is unreported in both captions (A03297-3 IHC caption; A30602 IHC caption). For IF/ICC or work across human, mouse and rat samples, choose A30602 based on its listed applications and reactivity; its supplied image documents human IHC only (A30602 catalog applications; A30602 catalog reactivity; A30602 IHC caption).
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 Cytoplasmic and nuclear tissue staining (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 fixation consistent across paraffin sections. (standard IHC practice; not target-specific); Caveat: Antibody staining and RNA show low consistency (HPA tissue IHC); Isoform / epitope: No isoforms; one 1–138 chain with no extracellular segment (UniProt); Regulation: Expression regulation not annotated (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.