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IL21R / Interleukin-21 receptor · IHC design guide
Design Immunohistochemistry for IL21R
Plan chromogenic IL21R IHC in paraffin sections using spleen as a documented positive tissue (HPA tissue IHC; datasheet A00808-1). Interpret cytoplasmic lymphoid staining with HPA's uncertain staining reliability and IL21R's membrane topology in mind (HPA tissue IHC; UniProt).
Evidence assembled Oct 2026 · For research use; verify linked source records and product datasheet before use
IL21R 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 in tissue IHC (HPA tissue IHC); membrane receptor (UniProt) | |
| Staining pattern | Cytoplasmic staining in lymphoid tissue cells (HPA tissue IHC) | |
| Antigen retrieval | EDTA pH 8.0 HIER, heat-mediated (datasheet A00808-1) | |
| Positive control | Bone marrow+3 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 sections (standard IHC practice; not target-specific) | |
| Caveat | Presumed off-target staining; verify cell specificity (HPA tissue IHC) | |
| Regulation | No regulation data in record (UniProt) | |
| Isoform / epitope | No isoforms listed; extracellular vs cytoplasmic epitope matters (UniProt) |
Section 1
Recommended IL21R IHC & IF Protocols
The catalog antibody’s IHC-P protocol (datasheet A00808-1) is followed by four published IL21R chromogenic IHC protocols (PMC11992169; PMC7390201; PMC5429142; PMC13376877).
| Sample | Paraffin-embedded human spleen tissue; fixative not specified (datasheet A00808-1) |
| Fixation | Image fixative and duration unreported (datasheet A00808-1); 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 A00808-1); 20 min, 95–100 °C (standard) |
| Peroxidase block | 3% H2O2, 10 min, room temperature (standard) |
| Blocking | 10% goat serum (datasheet A00808-1) |
| Primary antibody | Rabbit anti-IL21R, 2-5 μg/ml (datasheet A00808-1) |
| Primary incubation | Overnight at 4 °C (datasheet A00808-1) |
| Detection | HRP-conjugated secondary, DAB chromogen (datasheet A00808-1) |
| Counterstain | Hematoxylin, blue, dehydrate and mount (standard) |
| Expected result | IL21R-positive staining in hematopoietic cells of bone marrow (HPA tissue IHC: High). HPA tissue profile: Cytoplasmic expression in lymphoid tissues. No signal in the no-primary control. |
💡Decision noteStart with heat-mediated EDTA pH 8.0 (datasheet A00808-1). Use citrate pH 6.0 when following the liver or surgical-specimen protocols (PMC5429142; PMC13376877).
Section 2
What Is the Expected IL21R Staining Pattern?
IL21R is a membrane receptor with an extracellular region, one transmembrane segment and a cytoplasmic region (UniProt Q9HBE5 topology). In tissue IHC, expect staining in hematopoietic and lymphoid cell populations, often cytoplasmic (HPA: tissue IHC profile). Interpret apparent positives cautiously: HPA rates the tissue pattern Uncertain because antibody staining and RNA expression have low consistency, and presumed off-target staining was disregarded (HPA: tissue reliability).
| Clear staining in bone marrow hematopoietic cells or spleen red-pulp cells. | These are the strongest reported tissue IHC positives, both rated High (HPA: bone marrow and spleen). Assess the cell population and compartment together; a strong chromogen deposit alone does not establish IL21R specificity, given the Uncertain tissue reliability (HPA: tissue reliability). |
| Staining in lymph-node or tonsil germinal-center cells. | A Medium signal fits the reported tissue pattern (HPA: lymph node and tonsil). HPA describes tissue staining as cytoplasmic, while UniProt places IL21R in the membrane (HPA: tissue IHC profile; UniProt Q9HBE5 topology). Record the observed compartment instead of treating either location alone as definitive. |
| Predominantly nuclear staining, with no convincing signal in expected cell populations. | A nuclear pattern is outside the reported membrane and cytosol locations (UniProt Q9HBE5 subcellular location; HPA: ICC-IF subcellular location). Treat it as suspect and review the matched negative control, tissue morphology and detection background before scoring it as IL21R (general IHC practice). |
| Broad staining of adipocytes or respiratory epithelial cells, or colour deposited across many unrelated cells. | HPA reports IL21R as Not detected in adipocytes of adipose tissue and respiratory epithelial cells of bronchus (HPA: tissue IHC). Such staining may reflect cross-reactivity or endogenous detection activity; investigate with appropriate staining controls (general IHC practice). |
| No staining in bone marrow hematopoietic cells or spleen red-pulp cells. | Both are reported High positives (HPA: bone marrow and spleen), so first check tissue preservation, control performance and the staining workflow (general IHC practice). A negative result is not proof of absent IL21R: the tissue IHC profile itself has Uncertain reliability (HPA: tissue reliability). |
💡Expected IL21R appearanceCall a result plausible when hematopoietic or lymphoid cells show discernible, often cytoplasmic staining—High in bone marrow hematopoietic cells or spleen red-pulp cells, Medium in germinal-center cells—while widespread staining of HPA-undetected cell types is suspect (HPA: tissue IHC and Uncertain reliability).
| Topology and antibody epitope | IL21R spans the membrane at residues 233–253, with extracellular residues 20–232 and cytoplasmic residues 254–538 (UniProt Q9HBE5 topology). No epitope position is supplied, so topology cannot predict this antibody's exact IHC compartment. |
| Tissue evidence strength | HPA labels tissue IHC reliability Uncertain and reports presumed off-target binding that it disregarded (HPA: tissue reliability). Give the reported cell-level distribution more weight than isolated staining in an unexpected population. |
| IF/ICC Q: What location is reported? | A: Plasma membrane and cytosol are both approved ICC-IF locations (HPA: ICC-IF subcellular location). That finding can guide compartment review, but it does not establish an IHC paraffin-section protocol or validate a tissue-positive cell type. |
| Antigen retrieval | Retrieval is an optimization variable in paraffin IHC (general IHC practice). No supplied evidence establishes an IL21R-specific retrieval condition or effect; interpret changes alongside tissue and detection controls. |
| Glycosylation | UniProt lists 6 glycosylation sites in the extracellular region (UniProt Q9HBE5 glycosylation and topology). Their presence does not establish whether this antibody's epitope is affected in a paraffin section. |
| Situation | Likely cause | Next action |
|---|---|---|
| Expected positive tissue is blank. | The staining run may have failed, or signal may be below detection; HPA reports High staining in bone marrow hematopoietic cells and spleen red-pulp cells (HPA: tissue IHC). | Check a known-positive section processed in the same run, then review retrieval, primary-antibody use and detection steps against the validated IHC workflow (general IHC practice). |
| Signal appears mainly in nuclei. | Nuclei fall outside the supplied membrane and cytosol locations (UniProt Q9HBE5 subcellular location; HPA: ICC-IF subcellular location). | Compare the slide with a negative control and reassess whether nuclear colour is specific staining or detection artefact before reporting IL21R (general IHC practice). |
| Adipocytes or bronchial respiratory epithelium stain strongly. | Those cell types are reported Not detected, and HPA flags presumed off-target binding in the tissue dataset (HPA: tissue IHC and reliability). | Treat the finding as unconfirmed. Check cell identity and negative controls, and seek independent support before assigning the signal to IL21R (general IHC practice). |
| Diffuse colour obscures cell boundaries. | Background from detection chemistry, insufficient blocking or overly concentrated primary antibody can obscure a cellular pattern (general IHC practice). | Review negative-control staining and adjust blocking, washing or antibody concentration within the validated workflow; rescore only when cells and compartments are distinguishable (general IHC practice). |
| Germinal-center signal is weaker than splenic red-pulp signal. | That relative pattern is consistent with Medium staining in lymph-node and tonsil germinal centers versus High staining in spleen red pulp (HPA: tissue IHC). | Score each cell population against its reported level and the run's controls; avoid calling a Medium germinal-center result negative solely because spleen stains more strongly (HPA: tissue IHC; general IHC practice). |
| Membrane and cytoplasmic staining seem inconsistent. | UniProt describes a membrane receptor, HPA tissue IHC describes cytoplasmic expression, and HPA ICC-IF approves both plasma membrane and cytosol (UniProt Q9HBE5; HPA: tissue IHC and ICC-IF). | Document each compartment and cell type separately. Use tissue controls and the HPA Uncertain reliability rating when judging whether the pattern supports IL21R (HPA: tissue reliability; general IHC practice). |
Experiment evidence
IHC & IF images showing IL21R staining
A00808-1 · IHCIHC analysis of IL21R using anti-IL21R antibody (A00808-1). IL21R was detected in a paraffin-embedded section of human spleen tissue. Heat m
A00808-1 · IHCIHC analysis of IL21R using anti-IL21R antibody (A00808-1). IL21R was detected in a paraffin-embedded section of human prostate cancer tissu
HPA · Cerebral cortexHuman Protein Atlas IHC, Cerebral cortex. Source: https://www.proteinatlas.org/ENSG00000103522-IL21R/tissue/cerebral+cortex#imid_11477239
HPA · ColonHuman Protein Atlas IHC, Colon. Source: https://www.proteinatlas.org/ENSG00000103522-IL21R/tissue/colon#imid_11477173
HPA · LiverHuman Protein Atlas IHC, Liver. Source: https://www.proteinatlas.org/ENSG00000103522-IL21R/tissue/liver#imid_11477166
HPA · KidneyHuman Protein Atlas IHC, Kidney. Source: https://www.proteinatlas.org/ENSG00000103522-IL21R/tissue/kidney#imid_11477175
HPA · ICC-IF A-431Human Protein Atlas immunofluorescence, A-431, antibody HPA042296; green = IL21R, blue = nucleus, red = microtubules.
HPA · ICC-IF A-431Human Protein Atlas immunofluorescence, A-431, antibody HPA042296; green = IL21R, blue = nucleus, red = microtubules.
← swipe / scroll for more images →
Real IHC / IF data behind the staining-pattern expectations in this section.
Sample controls for IL21R IHC & IF
🧪Run spleen first and look for IL21R staining in red-pulp cells (HPA: High in spleen red-pulp cells). Use adipose tissue as the negative tissue, checking that adipocytes remain unstained (HPA: Not detected in adipocytes); on the spleen slide, cells outside the positive red-pulp population should remain at background.
Positive control tissue: Bone marrow (Hematopoietic cells, HPA High)
Negative control tissue: Adipose tissue (HPA Not detected)
ICC-IF cell lines (HPA subcellular resource): HPA ICC-IF images show IL21R in A-431, Rh30, U2OS, with annotated localisation: Plasma membrane (approved), Cytosol (approved) (HPA subcellular).
Technical controls: Include a no-primary, secondary-only slide, a host- and isotype-matched rabbit IgG control, and an IL21R knockout sample if available or cognate-peptide competition if the peptide is documented (selected IHC caption: rabbit primary; standard IHC specificity controls). Block endogenous peroxidase in spleen red pulp before HRP/DAB detection (selected IHC caption: HRP/DAB; standard IHC practice).
⚠️Feasibility: An IL21R-specific fixation window or fixation effect is unreported, and the selected A00808-1 paraffin-spleen caption does not report its fixative (selected IHC caption). That caption uses heat-mediated EDTA retrieval at pH 8.0 and 2 μg/ml primary antibody overnight at 4°C, but does not establish whether retrieval is essential (selected IHC caption). The supplied evidence does not establish whether frozen sections or IF are easier; HPA reports ICC-IF images and approved plasma-membrane and cytosol localization (HPA subcellular).
HPA tissue IHC evidence for IL21R
Comprehensive Human Protein Atlas IHC scoring per tissue (reliability: Uncertain — Low consistency between antibody staining and RNA expression data. Presumed off target binding observed and disregarded.). 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 |
|---|---|---|---|---|
| Bone marrow | Hematopoietic cells | High | Protein (IHC) | HPA → |
| Spleen | Cells in red pulp | High | Protein (IHC) | HPA → |
| Lymph node | Germinal center cells | Medium | Protein (IHC) | HPA → |
| Tonsil | Germinal center 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 → |
| Breast | Adipocytes | Not detected | Protein (IHC) | HPA → |
| Bronchus | Respiratory epithelial cells | Not detected | Protein (IHC) | HPA → |
| Caudate | Glial cells | Not detected | Protein (IHC) | HPA → |
Section 3
Advanced IL21R IHC Tips
Troubleshoot IL21R staining in paraffin sections by checking retrieval, cell identity, localisation and controls before scoring chromogenic signal.
How should I retrieve IL21R antigen in paraffin sections?
Start with heat-mediated antigen retrieval in EDTA at pH 8.0 (datasheet A00808-1). The selected spleen image used this retrieval before incubation with 2 μg/ml primary antibody overnight at 4°C; use that combination as a reference point, not proof that retrieval is optimal for every specimen (datasheet A00808-1). If staining is weak, check that sections were fully deparaffinised and that heating and cooling were consistent across slides before changing conditions (standard IHC practice). Compare any retrieval adjustment on adjacent sections with the same positive control, detection reagents and exposure to DAB, because processing differences can mimic a change in IL21R signal (standard IHC practice).
Could fixation explain weak or uneven IL21R staining?
Target-specific fixation sensitivity is unknown: the selected spleen caption describes a paraffin section but does not state its fixative (datasheet A00808-1). Record each specimen’s fixative and fixation duration, then compare similarly processed sections using the page’s EDTA pH 8.0 retrieval and identical staining conditions (standard IHC practice; datasheet A00808-1). If a batch stains unevenly, inspect tissue preservation and section thickness before attributing the difference to IL21R abundance (standard IHC practice). Keep a consistently processed spleen control in the run, since spleen is a reported site of IL21R expression, while recognising that its signal cannot establish a target-specific fixation requirement (UniProt Q9HBE5 tissue specificity; standard IHC practice).
Where should IL21R signal appear in an IHC section?
IL21R is a membrane receptor with an extracellular region at residues 20–232, one transmembrane segment at 233–253 and a cytoplasmic region at 254–538 (UniProt Q9HBE5 topology). Expect cell-associated signal and assess membranous and cytoplasmic patterns separately, since HPA reports plasma membrane and cytosol localisation (HPA subcellular). In spleen, compare stained cells with tissue architecture: HPA reports high staining in red-pulp cells, but rates its tissue-IHC profile uncertain because staining and RNA data have low consistency and presumed off-target staining occurred (HPA tissue IHC). A diffuse extracellular deposit should prompt review of detection controls and DAB development before it is scored as receptor staining (standard IHC practice).
How do epitope position and processing affect IL21R staining?
The supplied record lists 0 annotated isoforms, so there is no supplied isoform map on which to base a staining interpretation (UniProt Q9HBE5 isoforms). The mature receptor begins at residue 20; its extracellular region contains 6 listed glycosylation sites, whereas its cytoplasmic region spans residues 254–538 (UniProt Q9HBE5 processing, glycosylation and topology). The catalog antibody’s epitope is unspecified in the supplied caption, so do not assign its signal to either side of the membrane (datasheet A00808-1). If staining changes with retrieval, compare matched control sections and seek an epitope specification before claiming that glycosylation or cleavage caused the difference (standard IHC practice).
How should I follow up an IHC pattern with IL21R immunofluorescence?
Use IF as an independent localisation check and multiplex IL21R with a validated lymphoid-cell marker appropriate to the compartment being examined; the supplied record identifies lymphoid tissues as prominent expression sites (UniProt Q9HBE5 tissue specificity; standard IF practice). Choose fluorophores after measuring unstained-section autofluorescence, and include single-stain controls to assess spectral bleed-through (standard IF practice). Set permeabilisation according to the antibody’s confirmed epitope: an extracellular epitope may be accessible without it, whereas a cytoplasmic epitope requires access across the membrane (UniProt Q9HBE5 topology; standard IF practice). The supplied IHC caption does not specify the epitope or establish IF performance, so verify the antibody and fixation conditions for IF independently (datasheet A00808-1).
What controls help distinguish IL21R staining from chromogenic background?
Run a no-primary control to reveal signal from the detection system, and check peroxidase blocking before DAB development (standard IHC practice). The selected spleen image used 10% goat serum blocking, 2 μg/ml primary antibody overnight at 4°C, and peroxidase-conjugated secondary antibody for 30 minutes at 37°C (datasheet A00808-1). If background is widespread, compare sections with and without primary antibody, then adjust blocking, washing or detection development one variable at a time (standard IHC practice). Interpret low-level staining cautiously because HPA rates its tissue-IHC profile uncertain and reports presumed off-target binding (HPA tissue IHC).
How should I score IL21R-positive cells across tissue sections? ⚠ ANSWER MARKED FOR VERIFICATION
Define the compartment and cell population before scoring, then report percentage of positive cells and staining intensity as an H-score, or positive-cell density per mm² of evaluable tissue (standard IHC practice). Use the same threshold, DAB development and image settings across samples, and exclude folds, edges and necrotic regions from the measured area (standard IHC practice). Normalise counts to the relevant tissue area or eligible cell population rather than the whole section when tissue composition varies (standard IHC practice). Record membranous and cytoplasmic scores separately because both locations are reported, and flag that HPA tissue-IHC reliability is uncertain when comparing biological groups (HPA subcellular; HPA tissue IHC).
When is an IL21R-positive IHC result convincing?
A convincing result is reproducible in the same cell population, follows tissue architecture and exceeds the no-primary control under matched DAB development (standard IHC practice). Spleen is a reasonable positive-control tissue, but an isolated stained cell or region is insufficient because HPA reports uncertain tissue-IHC reliability and presumed off-target binding (UniProt Q9HBE5 tissue specificity; HPA tissue IHC). Review membranous and cytoplasmic signal against the reported plasma membrane and cytosol locations, without treating either pattern alone as proof of specificity (HPA subcellular). Edge staining, necrotic deposits or signal persisting without primary antibody should trigger a check for section artefact or endogenous peroxidase before scoring (standard IHC practice).
Boster reagents
Best IL21R / Interleukin-21 receptor IHC Antibodies
A00808-1 has real IHC data from human spleen and prostate cancer paraffin sections (catalog image captions); no IF/ICC data are supplied (catalog applications and images).
Real IHC data
Anti-IL21R Antibody ®
Cat # A00808-1
A00808-1 is human-reactive and listed for IHC (catalog: reactivity and applications). Its IHC captions show staining in human spleen and prostate cancer paraffin sections (catalog image captions).
Which to pick: Choose A00808-1 for human paraffin-section IHC: its spleen caption reports EDTA retrieval at pH 8.0 and 2 μg/ml primary antibody (A00808-1 IHC caption); the fixative is unreported (catalog image captions). No SKU is validated for IF/ICC here (catalog: applications and IF images). No SKU is supported for cross-species use because A00808-1 lists human reactivity only (catalog: reactivity).
Each figure is that product's own IHC / IF validation image from its datasheet.
References
- UniProt Consortium. UniProt entry Q9HBE5 (IL21R_HUMAN, Interleukin-21 receptor).
- Human Protein Atlas. IL21R tissue IHC expression (reliability: Uncertain).
- Human Protein Atlas. IL21R subcellular location (ICC-IF): Localized to the plasma membrane and cytosol..
- Human Protein Atlas. IL21R antibody validation summary (1 antibodies).
- Identification of M1 macrophage infiltration-related genes for immunotherapy in Her2-positive breast cancer based on bioinformatics analysis and machine learning. Scientific reports 2025 — PMC11992169.
- Prognostic value of novel immune-related genomic biomarkers identified in head and neck squamous cell carcinoma. Journal for immunotherapy of cancer 2020 — PMC7390201.
- A genome-wide association study identifies six novel risk loci for primary biliary cholangitis. Nature communications 2017 — PMC5429142.
- Incidence of B-cell Malignancies in Patients with Lung Cancer Receiving PD-1 Blockade Therapy. Clinical cancer research : an official journal of the American Association for Cancer Research 2026 — PMC13376877.
- PubMed PMID:11081504 — UniProt-cited evidence.
- PubMed PMID:11016959 — UniProt-cited evidence.
- PubMed PMID:12975309 — UniProt-cited evidence.
Immunohistochemistry protocol sheet for IL21R (Interleukin-21 receptor). Expected localisation Cytoplasmic in tissue IHC (HPA tissue IHC); membrane receptor (UniProt). Antigen retrieval: EDTA pH 8.0 HIER, heat-mediated (datasheet A00808-1). Validated IHC antibody: A00808-1 at 2-5 μg/ml (the product's own IHC validation image is shown). Controls (HPA): positive Bone marrow (Hematopoietic cells); negative Adipose tissue. IHC-P workflow on paraffin sections; fixative unspecified. Protocol steps: 1. Sample: Paraffin-embedded human spleen tissue; fixative not specified (datasheet A00808-1); 2. Fixation: Image fixative and duration unreported (datasheet A00808-1); 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 A00808-1); 20 min, 95–100 °C (standard); 6. Peroxidase block: 3% H2O2, 10 min , room temperature (standard); 7. Blocking: 10% goat serum (datasheet A00808-1); 8. Primary antibody: Rabbit anti-IL21R, 2-5 μg/ml (datasheet A00808-1); 9. Primary incubation: Overnight at 4 °C (datasheet A00808-1). Watch for: Fixation: Keep fixation consistent across sections (standard IHC practice; not target-specific); Caveat: Presumed off-target staining; verify cell specificity (HPA tissue IHC); Isoform / epitope: No isoforms listed; extracellular vs cytoplasmic epitope matters (UniProt); Regulation: No regulation data in record (UniProt). Evidence: UniProt Q9HBE5, HPA tissue IHC · Uncertain, HPA ICC-IF · plasma membrane and cytosol., Datasheet A00808-1, PMC11992169, PMC7390201. QR code links to https://www.bosterbio.com/bosterbio-gene-info-cards/IL21R/immunohistochemistry-ihc-guide.