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CNR2 / Cannabinoid receptor 2 · IHC design guide
Design Immunohistochemistry for CNR2
Plan chromogenic CNR2 IHC on paraffin sections with antibody A01307-3 at 1:10–1:50 (datasheet: IHC-P). Interpret variable cytoplasmic tissue staining alongside the expected membrane location and the uncertain tissue staining reliability (HPA tissue IHC; UniProt).
Evidence assembled Oct 2026 · For research use; verify linked source records and product datasheet before use
CNR2 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 | Variable cytoplasmic staining (HPA tissue IHC); membrane expected (UniProt) | |
| Staining pattern | Variable cytoplasmic staining in most tissues (HPA tissue IHC) | |
| Antigen retrieval | Citrate pH 6.0 HIER, 95–98 °C, 20 min (rule: cytoplasmic / membrane antigen) | |
| Positive control | Appendix+4 more · see all | |
| Negative control | Liver |
Important caveats
Reasons your staining may differ from the expected pattern.
| Fixation | FFPE human tissue shown (selected-SKU IHC image A01307-3); Matched tissue-IHC evidence does not establish the fixation claim. Validate the specimen-specific method before use. (selected-SKU IHC image A01307-3) | |
| Caveat | Antibody staining and RNA show low consistency (HPA tissue IHC) | |
| Regulation | Higher in B and NK cells; tonsil enriched (UniProt) | |
| Isoform / epitope | CB2A/CB2B differ only in 5′ UTR; C-tail is cytoplasmic (UniProt) |
Section 1
Recommended CNR2 IHC & IF Protocols
The catalog antibody’s IHC-P protocol (datasheet) is accompanied by published CNR2 staining protocols for mouse asthma sections (PMC8267324) and placental sections (PMC12984115).
| Sample | Paraffin-embedded tissue sections; fixative not specified (datasheet A01307-3; sample unspecified) |
| Fixation | Image fixative and duration unreported (datasheet A01307-3); 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-CNR2, 1:10-1:50 (datasheet A01307-3) |
| 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 | CNR2-positive staining in glandular cells of appendix (HPA tissue IHC: High). HPA tissue profile: Cytoplasmic expression at variable levels in most tissues. No signal in the no-primary control. |
💡Decision noteStart with citrate pH 6.0 at 95–98 °C for 20 min (page antigen retrieval); EDTA pH 8.0 was used for placental sections (PMC12984115 methods).
Section 2
What Is the Expected CNR2 Staining Pattern?
CNR2 is a seven-pass membrane receptor; UniProt also places it in dendrites and the perikaryon (UniProt P34972 topology and subcellular location). Immune cells are a plausible staining target, while HPA reports high IHC staining in lymph-node germinal-center cells and several epithelial cell types (UniProt P34972 tissue specificity; HPA tissue IHC). Interpret both compartments cautiously: HPA describes variable cytoplasmic staining across tissues and rates its tissue IHC profile Uncertain (HPA tissue IHC).
| Membrane-associated staining in lymph-node germinal-center cells, with cytoplasmic staining also visible. | This combines the receptor location predicted by its seven-pass topology with a cell population stained at High levels by HPA (UniProt P34972 topology; HPA: High in lymph-node germinal-center cells). Cytoplasmic staining resembles HPA's reported tissue profile, but the profile is Uncertain; neither appearance alone confirms CNR2 specificity (HPA tissue IHC). |
| Predominantly nuclear staining, without a convincing membrane-associated pattern. | A dominant nuclear pattern is unsupported by UniProt's membrane, dendrite and perikaryon locations and HPA's cytoplasmic tissue profile (UniProt P34972 subcellular location; HPA tissue IHC). Treat it as a possible artefact and compare it with staining produced when the primary antibody is omitted (general IHC practice). |
| Strong staining in an unexpected cell population or across nearly every cell. | Check cell identity before calling this CNR2: UniProt favors immune-system expression, whereas HPA reports variable staining in most tissues and rates the antibody evidence Uncertain (UniProt P34972 tissue specificity; HPA tissue IHC; HPA: CAB009719 IHC Uncertain). Cross-reactivity or endogenous detection activity is possible; a primary-omission control helps assess the latter (general IHC practice). |
| Diffuse color throughout tissue, including spaces between cells. | This is difficult to reconcile with a cellular membrane receptor or HPA's described cytoplasmic staining (UniProt P34972 topology; HPA tissue IHC). Background from detection chemistry or inadequate washing can obscure cell boundaries; assess the primary-omission control and review blocking and washes (general IHC practice). |
| No discernible staining in lymph-node germinal-center cells. | HPA records High staining in these cells, so absence raises a run-performance question, although that HPA result has Uncertain reliability (HPA: High in lymph-node germinal-center cells; HPA tissue IHC). Check tissue preservation, retrieval, antibody incubation and detection controls before interpreting another tissue as CNR2-negative (general IHC practice). |
💡Expected CNR2 appearanceA candidate positive result is cell-associated staining with a membrane-associated component in immune cells, including lymph-node germinal-center cells where HPA reports High staining; widespread nuclear color or diffuse intercellular color argues for artefact, and specificity remains Uncertain (UniProt P34972 topology and tissue specificity; HPA tissue IHC; general IHC practice).
| Seven-pass topology and epitope location (UniProt P34972 topology). | CNR2 spans the membrane seven times and has extracellular and cytoplasmic regions (UniProt P34972 topology). An antibody's epitope would affect which portion it recognizes, but the supplied record gives no epitope for CAB009719; do not infer a retrieval condition or a required staining compartment from epitope position (HPA antibody record; general IHC practice). |
| Tissue and cell selection (UniProt P34972 tissue specificity; HPA tissue IHC). | UniProt favors immune cells and reports especially high expression in tonsil; HPA reports High IHC staining in lymph-node germinal-center cells and multiple glandular populations (UniProt P34972 tissue specificity; HPA tissue IHC). These offer comparison sites, but HPA's Uncertain reliability limits their use as specificity controls (HPA tissue IHC). |
| Antibody and tissue-profile reliability (HPA antibody record; HPA tissue IHC). | HPA labels CAB009719 IHC Uncertain and reports low consistency between antibody staining and RNA expression (HPA antibody record; HPA tissue IHC). Score location and cell type alongside control slides, and describe an apparent positive as provisional when antibody specificity has not been independently established (general IHC practice). |
| Promoter-derived transcripts and processing (UniProt P34972 tissue specificity and processing). | The reported CB2A and CB2B transcripts differ only in their 5′ UTR, while the annotated protein chain is residues 1–360 (UniProt P34972 tissue specificity and processing). The supplied evidence therefore provides no protein-sequence basis for assigning an IHC signal to either transcript (UniProt P34972). |
| IF/ICC expectation (HPA subcellular record). | What should IF/ICC show? HPA summarizes the location as Membrane, but supplies no ICC-IF image-bearing cell lines or main-location entry (HPA subcellular record). A membrane-associated signal is plausible from UniProt topology; this record cannot establish an IF/ICC staining pattern or procedure (UniProt P34972 topology; HPA subcellular record). |
| Situation | Likely cause | Next action |
|---|---|---|
| Positive comparison tissue has no detectable signal. | The staining run may have failed; HPA's High lymph-node result is itself Uncertain (HPA tissue IHC). | Check that the expected cells are present, then review retrieval, primary incubation and detection controls before scoring the sample (general IHC practice). Do not treat an unstained comparison as proof of absent CNR2 (HPA tissue IHC). |
| Signal is chiefly nuclear. | A nuclear-dominant location is unsupported by the supplied CNR2 locations (UniProt P34972 subcellular location; HPA tissue IHC). | Inspect a primary-omission control and compare nuclear color with membrane and cytoplasmic staining in the same section (general IHC practice). Record the pattern as discordant rather than assigning it to CNR2 (UniProt P34972; HPA tissue IHC). |
| Color appears in nearly all cells and between cells. | Diffuse background or endogenous detection activity may be contributing (general IHC practice). | Review blocking and washes, and run a primary-omission control to assess detection-derived color (general IHC practice). Reassess whether any cell-associated pattern remains; HPA's variable cytoplasmic profile alone cannot validate a diffuse result (HPA tissue IHC). |
| Liver cholangiocytes stain strongly. | HPA lists cholangiocytes as Not detected, although its overall tissue IHC reliability is Uncertain (HPA: liver cholangiocytes Not detected; HPA tissue IHC). | Confirm the cell identification and inspect controls for background or endogenous activity before calling the signal CNR2 (general IHC practice). Treat the discrepancy as a reason to investigate specificity, not as a definitive exclusion (HPA tissue IHC). |
| Glandular staining exceeds immune-cell staining. | That distribution can match HPA's High glandular-cell observations, while differing from UniProt's preferential immune-cell expression (HPA tissue IHC; UniProt P34972 tissue specificity). | Score each cell population separately and report the source disagreement (general IHC practice; HPA tissue IHC; UniProt P34972 tissue specificity). Avoid resolving it by intensity alone because HPA rates the tissue staining Uncertain (HPA tissue IHC). |
| A staining change follows a retrieval adjustment. | Target-specific fixation effects are not established by the supplied assay evidence. Verify with a matched IHC source before attributing a result to fixation. | Compare adjacent sections with the same controls and document the retrieval conditions and cellular pattern (general IHC practice). Describe the change as an assay observation; do not attribute it to CNR2 epitope masking without separate evidence (general IHC practice). |
Experiment evidence
IHC & IF images showing CNR2 staining
A01307-3 · IHCImmunohistochemical analysis of paraffin-embedded R. brain section using CB2 Antibody(C-term). A01307-3 was diluted at 1:25 dilution. A pero
A01307-3 · IHCImmunohistochemical analysis of paraffin-embedded H. brain section using CB2 Antibody(C-term). A01307-3 was diluted at 1:25 dilution. A pero
HPA · Cerebral cortexHuman Protein Atlas IHC, Cerebral cortex. Source: https://www.proteinatlas.org/ENSG00000188822-CNR2/tissue/cerebral+cortex#imid_3372240
HPA · ColonHuman Protein Atlas IHC, Colon. Source: https://www.proteinatlas.org/ENSG00000188822-CNR2/tissue/colon#imid_3369942
HPA · LiverHuman Protein Atlas IHC, Liver. Source: https://www.proteinatlas.org/ENSG00000188822-CNR2/tissue/liver#imid_3369943
HPA · KidneyHuman Protein Atlas IHC, Kidney. Source: https://www.proteinatlas.org/ENSG00000188822-CNR2/tissue/kidney#imid_3369936
← swipe / scroll for more images →
Real IHC / IF data behind the staining-pattern expectations in this section.
Sample controls for CNR2 IHC & IF
🧪Run lymph node first and expect staining in germinal center cells (HPA: High in germinal center cells). Use liver cholangiocytes as the negative tissue (HPA: Not detected); on the lymph node slide, assess cells outside the germinal centers for background, without assuming they are CNR2-negative.
Positive control tissue: Appendix (Glandular cells, HPA High)
Negative control tissue: Liver (HPA Not detected)
ICC-IF cell lines (HPA subcellular resource): HPA carries no ICC-IF cell line for CNR2; derive a cell-line control from the positive tissue's cell type (Glandular cells) and confirm it by RNA or western blot first.
Technical controls: Include a no-primary (secondary-only) control, a host-species-, immunoglobulin-class-, and clonality-matched isotype control where applicable, and CNR2-knockout tissue as a biological negative (standard IHC practice). For chromogenic lymph node IHC, quench endogenous peroxidase and check background in the control slides (standard IHC practice).
⚠️Feasibility: No matched evidence reports a CNR2-specific fixation window or fixation effect, and the fixative is unreported in the A01307-3 paraffin-section caption (selected tissue-IHC caption). Antigen-retrieval dependence and whether frozen sections or IF are easier are unreported; assess retrieval conditions empirically on matched sections (standard IHC practice). In lymph node, endogenous peroxidase in immune cells can contribute to chromogenic background (standard IHC practice).
HPA tissue IHC evidence for CNR2
Comprehensive Human Protein Atlas IHC scoring per tissue (reliability: Uncertain — 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 |
|---|---|---|---|---|
| Appendix | Glandular cells | High | Protein (IHC) | HPA → |
| Breast | Glandular cells | High | Protein (IHC) | HPA → |
| Colon | Glandular cells | High | Protein (IHC) | HPA → |
| Duodenum | Glandular cells | High | Protein (IHC) | HPA → |
| Lymph node | Germinal center cells | 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 CNR2 IHC Tips
Use matched controls and compartment-aware scoring to assess CNR2 staining in paraffin sections; published tissue patterns warrant cautious interpretation (HPA: reliability uncertain).
What retrieval should I start with for CNR2 paraffin IHC?
Start with citrate buffer at pH 6.0 for heat-induced retrieval at 95–98 °C for 20 min (page retrieval setting). Allow sections to cool in buffer, then wash before blocking so handling is consistent across slides (standard IHC practice). If staining is weak, compare a short retrieval-time series on matched sections while holding antibody concentration and detection constant (standard IHC practice). Include a known positive tissue section and a no-primary control in each comparison; high CNR2 staining has been reported in lymph-node germinal center cells, although the tissue IHC reliability is uncertain (HPA: tissue IHC).
How should I troubleshoot fixation-related loss of CNR2 staining?
The selected antibody caption describes paraffin-embedded brain but does not report its fixative, so CNR2 sensitivity to fixation is unknown for this assay (A01307-3 tissue-IHC caption). Record fixative, fixation duration, processing schedule and section age for each specimen before comparing signal intensity (standard IHC practice). For new material, keep those conditions consistent across experimental and control tissues, then compare matched sections using the same citrate pH 6.0 retrieval for 20 min (page retrieval setting; standard IHC practice). If staining varies, test processing batches side by side with the same detection run before attributing differences to CNR2 abundance (standard IHC practice).
Which staining compartments should count as plausible CNR2 signal?
Assess membrane-associated staining first because CNR2 is a 7-pass receptor annotated at the cell membrane (UniProt P34972 topology and localisation). Perikaryal and dendritic staining can also be plausible, including apical dendrites of pyramidal neurons, but assign cell identity from morphology or a companion marker (UniProt P34972 localisation; standard IHC practice). Diffuse cytoplasmic staining occurs across many tissues in the HPA survey, whose antibody staining has low consistency with RNA expression (HPA: tissue IHC, reliability uncertain). Compare compartment patterns with the no-primary control and tissue architecture before scoring a broadly cytoplasmic reaction as specific (standard IHC practice).
Can this stain distinguish CB2A from CB2B or reveal an inaccessible epitope?
CB2A and CB2B arise through alternative promoter usage and differ in their 5′ UTR, so a protein stain cannot distinguish them on that basis (UniProt P34972 tissue specificity). The catalog image names a C-terminal antibody, but the caption does not map its precise epitope (A01307-3 tissue-IHC caption). CNR2 residues 302–360 face the cytoplasm, whereas residues 1–33 are extracellular and include a glycosylation site at 11 (UniProt P34972 topology and glycosylation). If staining changes with retrieval, compare matched controls and seek epitope-mapping data before assigning the change to glycosylation or C-terminal phosphorylation (UniProt P34972 modified residues; standard IHC practice).
How should I check CNR2 by multiplex IF after chromogenic IHC?
Treat IF as a separate assay: the selected caption documents paraffin-section DAB IHC, and no HPA ICC/IF images are listed (A01307-3 tissue-IHC caption; HPA: subcellular). Multiplex CNR2 with a validated marker for the cell population under study, checking whether receptor signal follows expected cellular boundaries (UniProt P34972 localisation; standard IF practice). Choose a fluorophore channel away from the specimen's strongest autofluorescence and inspect unstained and single-label controls before interpreting overlap (standard IF practice). For a confirmed intracellular C-terminal epitope, assess mild permeabilisation against a matched untreated section; confirm epitope location before assuming this antibody recognizes residues 302–360 (UniProt P34972 topology; standard IF practice).
How can I separate CNR2 DAB signal from section background?
The selected paraffin-section image used A01307-3 at 1:25, a peroxidase-conjugated secondary at 1:400 and DAB detection (A01307-3 tissue-IHC caption). For background troubleshooting, compare a no-primary slide, a secondary-only slide and a primary-dilution series on adjacent sections (standard IHC practice). Block endogenous peroxidase before detection, control incubation and wash conditions, and inspect unstained pigment or precipitate before calling brown deposits positive (standard chromogenic IHC practice). Because HPA reports variable cytoplasmic staining with uncertain reliability, require cellular morphology and a signal above local control background rather than judging color alone (HPA: tissue IHC; standard IHC practice).
How should I quantify CNR2 staining across tissue groups? ⚠ ANSWER MARKED FOR VERIFICATION
Define the scored cell population and compartment before analysis, then apply those definitions to every slide (standard IHC practice; UniProt P34972 localisation). For cellular staining, report the percentage of positive cells and an H-score using intensity categories 0–3; for sparse labelled cells, report positive-cell density per mm² (standard IHC practice). Normalise counts to viable tissue area or the number of eligible cells, and use the same exposure, stain development and threshold rules across batches (standard IHC practice). Report membrane-associated and diffuse cytoplasmic scores separately because HPA describes variable cytoplasmic staining with uncertain tissue-IHC reliability (UniProt P34972 localisation; HPA: tissue IHC).
When should I doubt an apparent CNR2-positive result?
Question signal confined to tissue edges, folds or necrotic regions, or staining that persists on a no-primary slide (standard IHC practice). Check peroxidase blocking when DAB deposits follow blood-rich or enzyme-rich structures rather than intact cell outlines (standard chromogenic IHC practice). Strong staining assigned to a cell population should be compared with its morphology and controls: CNR2 is preferentially expressed in immune cells, whereas HPA tissue-IHC patterns have uncertain reliability (UniProt P34972 tissue specificity; HPA: tissue IHC). Membrane, perikaryal and dendritic patterns are biologically plausible, but an isolated, structureless deposit does not establish receptor localisation (UniProt P34972 localisation; standard IHC practice).
Boster reagents
Best CNR2 / Cannabinoid receptor 2 IHC Antibodies
A01307-3 is a human-reactive CNR2 IHC-P antibody (catalog: applications and reactivity), with IHC images of paraffin-embedded R. and H. brain and paraffin-section, paraffin-embedded human skin carcinoma (catalog: IHC captions).
Real IHC data
Anti-CB2 Antibody (C-term)
Cat # A01307-3
A01307-3 is listed for human IHC-P and has a DAB image of a paraffin-embedded R. brain section at 1:25 (catalog: applications and reactivity; R. brain caption). Its other IHC captions show paraffin-embedded H. brain and paraffin-section, paraffin-embedded human skin carcinoma (catalog: IHC captions).
Which to pick: For paraffin-section IHC, choose the rabbit polyclonal A01307-3; its listed IHC-P dilution is 1:10–1:50, and the brain captions do not report a fixative (catalog: host, clonality, dilution and brain captions). No listed SKU supports an IF/ICC choice because A01307-3 has neither IF/ICC in its application list nor an IF image (catalog: applications and IF image alts). For cross-species work, the R. brain image alone does not establish listed reactivity beyond Human (catalog: R. brain caption and reactivity).
Each figure is that product's own IHC / IF validation image from its datasheet.
References
- UniProt Consortium. UniProt entry P34972 (CNR2_HUMAN, Cannabinoid receptor 2).
- Human Protein Atlas. CNR2 tissue IHC expression (reliability: Uncertain).
- Human Protein Atlas. CNR2 subcellular location (ICC-IF): Membrane.
- Human Protein Atlas. CNR2 antibody validation summary (1 antibodies).
- Cannabinoid type 2 receptors in dopamine neurons inhibits psychomotor behaviors, alters anxiety, depression and alcohol preference. Scientific reports 2017 — PMC5727179.
- Selective activation of cannabinoid receptor 2 regulates Treg/Th17 balance to ameliorate neutrophilic asthma in mice. Annals of translational medicine 2021 — PMC8267324.
- Altered Endocannabinoid Signaling in Placentas from SARS-CoV-2-Infected Pregnancies. Diagnostics (Basel, Switzerland) 2026 — PMC12984115.
- Cannabinoid CB2 receptor potentiates obesity-associated inflammation, insulin resistance and hepatic steatosis. PloS one 2009 — PMC2688760.
- PubMed PMID:7689702 — UniProt-cited evidence.
- PubMed PMID:19496827 — UniProt-cited evidence.
- PubMed PMID:16710414 — UniProt-cited evidence.
Immunohistochemistry protocol sheet for CNR2 (Cannabinoid receptor 2). Expected localisation Variable cytoplasmic staining (HPA tissue IHC); membrane expected (UniProt). Antigen retrieval: Citrate pH 6.0 HIER, 95–98 °C, 20 min (rule: cytoplasmic / membrane antigen). Validated IHC antibody: A01307-3 at 1:10-1:50 (the product's own IHC validation image is shown). Controls (HPA): positive Appendix (Glandular cells); negative Liver. IHC workflow; specimen preparation unspecified. Protocol steps: 1. Sample: Paraffin-embedded tissue sections; fixative not specified (datasheet A01307-3; sample unspecified); 2. Fixation: Image fixative and duration unreported (datasheet A01307-3); 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-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-CNR2, 1:10-1:50 (datasheet A01307-3); 9. Primary incubation: Overnight at 4 °C (standard). Watch for: Fixation: FFPE human tissue shown (selected-SKU IHC image A01307-3); Matched tissue-IHC evidence does not establish the fixation claim. Validate the specimen-specific method before use. (selected-SKU IHC image A01307-3); Caveat: Antibody staining and RNA show low consistency (HPA tissue IHC); Isoform / epitope: CB2A/CB2B differ only in 5′ UTR; C-tail is cytoplasmic (UniProt); Regulation: Higher in B and NK cells; tonsil enriched (UniProt). Evidence: UniProt P34972, HPA tissue IHC · Uncertain, HPA ICC-IF · Membrane, Datasheet A01307-3, PMC8267324, PMC12984115. QR code links to https://www.bosterbio.com/bosterbio-gene-info-cards/CNR2/immunohistochemistry-ihc-guide.