ADORA2A / Adenosine receptor A2a · IHC design guide

Design Immunohistochemistry for ADORA2A

Plan chromogenic ADORA2A IHC on paraffin sections with the catalog antibody at 1:25 (datasheet M02268). Use caudate neuronal projections as a staining reference (HPA tissue IHC), while treating membrane localization as a molecular expectation (UniProt).

Evidence assembled Oct 2026 · For research use; verify linked source records and product datasheet before use

Immunohistochemistry protocol sheet for ADORA2A (IHC for ADORA2A): expected localisation Cell membrane expected (UniProt); caudate neuronal projections stain (HPA tissue IHC), antibody M02268, validated IHC image, and IHC protocol steps — Printable **ADORA2A** IHC protocol sheet — expected localisation Cell membrane expected (UniProt); caudate neuronal projections stain (HPA tissue IHC), antibody M02268, controls and protocol steps. Open the full ADORA2A IHC guide →

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ADORA2A 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	Cell membrane expected (UniProt); caudate neuronal projections stain (HPA tissue IHC)
	Staining pattern	Caudate neuronal projections and a subset of thymic cells (HPA tissue IHC)
	Antigen retrieval	Citrate pH 6 HIER, heat-mediated (datasheet M02268)
	Positive control ⓘ	Appendix+4 more · see all
	Negative control ⓘ	Adipose tissue+4 more · see all

Important caveats

Reasons your staining may differ from the expected pattern.

	Fixation	Formaldehyde-fixed paraffin sections were used (datasheet M02268). (selected-SKU IHC image M02268)
	Caveat	Antibody staining and RNA show medium consistency (HPA tissue IHC)
	Regulation	Expression regulation is unreported (UniProt)
	Isoform / epitope	No isoforms annotated; extracellular versus cytoplasmic epitope location matters (UniProt)

Section 1

Recommended ADORA2A IHC & IF Protocols

The catalog antibody’s IHC-P protocol is paired with one published ADORA2A IHC protocol from a prostate adenocarcinoma cohort (PMC9827409).

Recommended immunohistochemistry (IHC-P) protocol parameters
Sample	Formaldehyde-fixed, paraffin-embedded Human heart tissue (datasheet M02268)
Fixation	Image formalin-fixed; duration unreported (datasheet M02268); verify before use.
Sectioning	4–5 µm sections on charged slides (standard)
Deparaffinisation	Xylene, graded ethanol series to water (standard)
Antigen retrieval	Heat retrieval: Citrate pH 6 (datasheet M02268); 20 min, 95–100 °C (standard)
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-ADORA2A, 1:25 (datasheet M02268)
Primary incubation	1 hours at 37°C (datasheet M02268)
Detection	HRP-polymer secondary, DAB chromogen 5–10 min (standard)
Counterstain	Hematoxylin, blue, dehydrate and mount (standard)
Expected result	ADORA2A-positive staining in endocrine cells of appendix (HPA tissue IHC: High). HPA tissue profile: Expression in caudate nucleus and a subset of cells in thymus. No signal in the no-primary control.

💡Decision noteStart with citrate pH 6 heat retrieval for the catalog antibody (datasheet M02268). The published protocol used EDTA pH 9 microwave retrieval (PMC9827409 methods).

Section 2

What Is the Expected ADORA2A Staining Pattern?

ADORA2A is a 7-transmembrane receptor at the cell membrane, including neuronal processes (UniProt P29274 topology and localization). In paraffin IHC, expect staining in caudate neuronal projections and selected endocrine cells of the appendix and intestine (HPA: High). Bone marrow hematopoietic cells show Medium staining (HPA: Medium). HPA rates its tissue IHC profile Enhanced, while reporting medium consistency with RNA expression (HPA: tissue IHC reliability).

What am I looking at on my slide?
Strong staining follows caudate neuronal projections or marks scattered intestinal endocrine cells (HPA: High).	This matches the reported cell-specific pattern (HPA: tissue IHC). Assess the relevant cells and structures; widespread staining of every cell is not the expected positive result (HPA: tissue IHC profile).
The dominant signal is nuclear, with little staining at cell boundaries or neuronal processes.	A nuclear-dominant pattern does not match the membrane localization (UniProt P29274; HPA: plasma membrane, ICC-IF). Review morphology and controls before scoring it as ADORA2A.
Most cells stain in a tissue where HPA reports a restricted positive cell population.	Consider antibody cross-reactivity or endogenous chromogenic activity (general IHC practice). HPA reports endocrine cells in appendix and intestine and a subset of thymus cells, rather than uniform staining (HPA: tissue IHC).
Color spreads across the section without clear cell borders or a recognizable positive population.	Diffuse background cannot establish the expected pattern (HPA: tissue IHC; UniProt P29274 localization). Check the detection and background controls, then judge signal in the annotated cell type (general IHC practice).
No signal appears in caudate neuronal projections or intestinal endocrine cells (HPA: High).	First check that the relevant structures are present in the section (HPA: tissue IHC). If they are, review retrieval, detection and reagent performance using controls (general IHC practice); absence alone does not establish biological loss.

💡Expected ADORA2A appearanceCall a result positive when distinct membrane-associated signal marks caudate neuronal projections or selected intestinal endocrine cells at High intensity (UniProt P29274 localization; HPA: High); dominant nuclear or uniform tissue-wide color is suspect (HPA: tissue IHC profile).

How each factor affects the staining
Membrane topology and compartment	ADORA2A has 7 transmembrane segments and a cytoplasmic C-terminal region (UniProt P29274 topology). Interpret chromogenic signal against cell borders and neuronal projections; topology alone does not predict a staining dilution or retrieval setting.
Cell-specific reference pattern	HPA reports High staining in caudate neuronal projections and endocrine cells of appendix, colon, duodenum, rectum and small intestine; bone marrow hematopoietic cells are Medium (HPA: tissue IHC). Score the named cells, not the whole tissue.
Strength of the IHC reference	The tissue profile is rated Enhanced but has medium consistency with RNA data (HPA: tissue IHC reliability). Two listed antibodies have Enhanced IHC validation, while one is Supported (HPA: antibody validation); these ratings do not validate every new assay condition.
Glycosylation and processing	UniProt lists 1 glycosylation site at residue 154 and a single 1–412 chain, with no signal peptide or propeptide annotated (UniProt P29274). These annotations do not establish an IHC epitope, shedding pattern or fixation sensitivity.
IF/ICC: what localization is expected?	Mainly plasma membrane, with additional vesicle and primary-cilium localization (HPA: approved ICC-IF locations). This is an interpretation reference for the separate IF/ICC guide; the paraffin IHC pattern remains anchored to HPA tissue staining.

Why is my staining missing, weak or wrong?
Situation	Likely cause	Next action
A known-positive section is blank.	The sampled section may lack the relevant cells, or the IHC workflow may have failed (HPA: tissue IHC; general IHC practice).	Confirm caudate projections or intestinal endocrine cells are present; check detection controls and the catalog antibody’s IHC-P instructions (HPA: High; general IHC practice).
Signal is mainly nuclear.	Nuclear-dominant staining conflicts with the reported membrane localization (UniProt P29274; HPA: approved plasma membrane ICC-IF).	Review morphology, negative controls and antibody specificity before interpreting the signal as ADORA2A (general IHC practice).
Nearly all cells stain strongly.	The distribution exceeds HPA’s selected endocrine cells and neuronal projections; cross-reactivity or nonspecific detection is possible (HPA: tissue IHC; general IHC practice).	Compare the staining with cell morphology and a negative control; judge intensity within HPA’s named positive populations (HPA: tissue IHC; general IHC practice).
Color appears without primary antibody.	Endogenous activity or nonspecific detection can produce chromogenic signal (general IHC practice).	Address the implicated detection background and repeat the negative control before scoring tissue staining (general IHC practice).
Diffuse background obscures the positive population.	Poor signal-to-background separation prevents reliable assessment of the restricted HPA pattern (HPA: tissue IHC; general IHC practice).	Review blocking, antibody dilution, washing and detection conditions, then reassess the named cells (general IHC practice; HPA: tissue IHC).
An HPA-negative cell population stains.	For example, adipocytes in adipose tissue are Not detected by HPA; staining there warrants specificity review (HPA: adipose adipocytes, Not detected).	Check controls and morphology before calling it ADORA2A; a reference negative does not by itself diagnose the source of unexpected color (general IHC practice).

Source: UniProt P29274 Human Protein Atlas tissue Human Protein Atlas subcellular

Experiment evidence

IHC & IF images showing ADORA2A staining

M02268 staining ADORA2A in Human heart tissue sections by Immunohistochemistry (IHC-P -paraformaldehyde-fixed, paraffin-embedded sections). Tissue was fixed with formaldehyde and blocked with 3% BSA for 0. 5 hour at room temperature; antigen retrieval was by heat mediation with a citrate buffer (pH6). Samples were incubated with primary antibody (1/25) for 1 hours at 37°C. A undiluted biotinylated goat polyvalent antibody was used as the secondary antibody.

M02268 · IHCM02268 staining ADORA2A in Human heart tissue sections by Immunohistochemistry (IHC-P -paraformaldehyde-fixed, paraffin-embedded sections).

HPA · Cerebral cortexHuman Protein Atlas IHC, Cerebral cortex. Source: https://www.proteinatlas.org/ENSG00000128271-ADORA2A/tissue/cerebral+cortex#imid_20537651

HPA · CaudateHuman Protein Atlas IHC, Caudate. Source: https://www.proteinatlas.org/ENSG00000128271-ADORA2A/tissue/basal+ganglia#imid_1213

HPA · ColonHuman Protein Atlas IHC, Colon. Source: https://www.proteinatlas.org/ENSG00000128271-ADORA2A/tissue/colon#imid_20537569

HPA · LiverHuman Protein Atlas IHC, Liver. Source: https://www.proteinatlas.org/ENSG00000128271-ADORA2A/tissue/liver#imid_20537578

HPA · ICC-IF HEK293Human Protein Atlas immunofluorescence, HEK293, antibody HPA075997; green = ADORA2A, blue = nucleus, red = microtubules.

← swipe / scroll for more images →

Real IHC / IF data behind the staining-pattern expectations in this section.

Sample controls for ADORA2A IHC & IF

🧪Run appendix first: endocrine cells should stain strongly (HPA: High in appendix endocrine cells). Use adipose tissue as the negative tissue, focusing on adipocytes (HPA: Not detected in adipocytes); neighboring non-endocrine cells on the appendix slide should provide an internal background comparison, with less staining than the endocrine cells.

Positive control tissue: Appendix (Endocrine cells, HPA High)

Negative control tissue: Adipose tissue (HPA Not detected)

ICC-IF cell lines (HPA subcellular resource): HPA ICC-IF images show ADORA2A in HEK293, ASC52telo, RPTEC/TERT1, hTERT-RPE1 (serum starved), with annotated localisation: Plasma membrane (approved) (HPA subcellular).

Technical controls: Include a no-primary (secondary-only) control, a host- and isotype-matched control appropriate to the primary antibody, and ADORA2A knockout material as a biological negative (standard IHC practice). For appendix sections, quench endogenous peroxidase and check for endogenous biotin background when using biotinylated detection (standard IHC practice; M02268 caption: biotinylated secondary antibody).

⚠️Feasibility: A target-specific fixation window or fixation effect is unreported, and the selected M02268 caption's fixative is listed as unreported (M02268 caption metadata: fixative not stated). Heat-mediated citrate retrieval at pH 6 is described, but retrieval dependence is unreported (M02268 caption: citrate buffer, pH 6). No supplied evidence establishes that frozen sections or IF are easier; IF localisation can be assessed against plasma-membrane staining, while endogenous peroxidase or biotin background may complicate appendix IHC (HPA: approved plasma-membrane location; standard IHC practice).

HPA tissue IHC evidence for ADORA2A

Comprehensive Human Protein Atlas IHC scoring per tissue (reliability: Enhanced — Medium consistency between antibody staining and RNA expression data.). Rows are taken directly from the HPA tissue chart — click any row's HPA link to view the source.

Positive expression · recommended positive controls

Tissue	Cell type	Level	Evidence	Source
Appendix	Endocrine cells	High	Protein (IHC)	HPA →
Caudate	Neuronal projections	High	Protein (IHC)	HPA →
Colon	Endocrine cells	High	Protein (IHC)	HPA →
Duodenum	Endocrine cells	High	Protein (IHC)	HPA →
Rectum	Endocrine cells	High	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 →
Cerebral cortex	Endothelial cells	Not detected	Protein (IHC)	HPA →

Section 3

Advanced ADORA2A IHC Tips

Use the catalog antibody’s IHC-P conditions as a starting point, then assess ADORA2A staining by cell type and compartment.

How should I retrieve ADORA2A in paraffin sections without losing membrane detail?

Use heat-mediated antigen retrieval in citrate buffer at pH 6 for ADORA2A paraffin sections (datasheet M02268). Begin with the catalog antibody’s documented conditions, then keep heating and cooling times consistent across slides so staining comparisons remain interpretable (standard IHC practice). If staining is weak, vary retrieval time in small steps while checking whether membrane outlines and tissue structure remain intact (standard IHC practice). The receptor has 7 transmembrane segments, so assess staining in cellular context rather than treating diffuse color as sufficient evidence (UniProt P29274 topology). Run a known positive control alongside each retrieval condition, such as caudate neuronal projections (HPA: High in caudate neuronal projections).

Could fixation explain weak ADORA2A staining in my paraffin sections?

Target-specific fixation sensitivity for ADORA2A is unknown from the supplied evidence; establish it experimentally before attributing weak staining to fixation. Record fixative, fixation duration, tissue thickness and processing history for each specimen, then compare sections processed together (standard IHC practice). Apply the documented citrate retrieval at pH 6 consistently before changing other variables (datasheet M02268). Include a positive tissue control in each run; caudate neuronal projections provide an evidence-based reference for detectable staining (HPA: High in caudate neuronal projections). If control staining also falls, investigate processing, retrieval and detection together rather than assigning a target-specific fixation mechanism (standard IHC practice).

What staining pattern should I expect for ADORA2A in tissue IHC?

Prioritize membrane-associated staining when assessing ADORA2A, which is annotated at the cell membrane (UniProt P29274 subcellular location). Neuronal-process staining can also be relevant: the receptor colocalizes with GAS2L2 at neuronal processes, and HPA reports high staining in caudate neuronal projections (UniProt P29274 subcellular location; HPA: High in caudate neuronal projections). HPA also reports medium cytoplasmic or membrane staining in cerebellar molecular-layer cells, so evaluate morphology and cell identity together (HPA: Medium in cerebellar molecular-layer cells). Compare staining with a matched negative control and nearby tissue structure before scoring faint cytoplasmic color (standard IHC practice). Do not assign a compartment from chromogen alone when cell boundaries are unclear (standard IHC practice).

How does epitope position affect ADORA2A staining after retrieval?

Map the catalog antibody’s stated immunogen or epitope before interpreting retrieval-dependent staining; its position is not supplied here. ADORA2A has 7 transmembrane segments and a cytoplasmic C-terminal region spanning residues 291–412 (UniProt P29274 topology). An extracellular epitope and a cytoplasmic epitope can differ in accessibility after fixation and retrieval, so compare conditions empirically (standard IHC practice). UniProt lists one glycosylation site at residue 154 and no annotated isoforms; neither fact establishes how this antibody binds processed tissue (UniProt P29274 glycosylation and isoforms). Keep antibody concentration and detection conditions fixed while evaluating retrieval changes against a positive control (standard IHC practice).

How should I adapt the ADORA2A IHC findings to multiplex IF?

Optimize IF independently of the chromogenic IHC-P conditions documented for M02268, including its citrate retrieval at pH 6 (datasheet M02268). Pair ADORA2A with a marker identifying the expected cells, such as a neuronal marker when examining caudate projections (HPA: High in caudate neuronal projections). Choose fluorophores after checking tissue autofluorescence; a spectrally separated far-red channel can help when background is strong at shorter wavelengths (standard IF practice). Set permeabilisation according to the antibody’s verified epitope: a cytoplasmic-facing epitope requires access across the membrane, whereas an extracellular-facing epitope may not (UniProt P29274 topology; standard IF practice). Include single-stain and no-primary controls to assess bleed-through and background (standard IF practice).

How can I reduce diffuse ADORA2A chromogen background?

Check a no-primary control first to distinguish primary-antibody-associated color from detection-system or tissue background (standard IHC practice). The selected tissue-IHC caption used a 3% BSA block for 0.5 hour at room temperature and primary antibody at 1:25 for 1 hour at 37°C (M02268 tissue-IHC caption). Treat those as documented conditions for that image, then titrate the primary antibody and wash thoroughly if diffuse color obscures cellular detail (standard IHC practice). With peroxidase detection, block endogenous peroxidase and inspect a detection-only control before judging DAB signal (standard IHC practice). Compare any remaining color with the expected membrane-associated pattern and tissue morphology (UniProt P29274 subcellular location; standard IHC practice).

How should I quantify ADORA2A staining across paraffin sections? ⚠ ANSWER MARKED FOR VERIFICATION

Define the tissue region, eligible cell type and membrane-staining threshold before reviewing outcome groups (standard IHC practice; UniProt P29274 subcellular location). For discrete cells, record the percentage positive and staining intensity as an H-score; for neuronal projections, measure positive area or process density per mm² within a defined region (standard IHC practice; HPA: High in caudate neuronal projections). Normalize cell counts to eligible cells and projection measurements to analyzable tissue area, excluding folds, tears and necrosis consistently (standard IHC practice). Keep section thickness, retrieval, imaging and chromogen development comparable across cases (standard IHC practice). Review representative positive and negative controls before applying thresholds to the full set (standard IHC practice).

When is apparent ADORA2A positivity more likely to be artefact?

A convincing result fits the examined cell type and a plausible membrane-associated pattern, rather than relying on stain intensity alone (UniProt P29274 subcellular location; standard IHC practice). Caudate neuronal projections and selected intestinal endocrine cells have high HPA staining, providing context for assessing these cell types (HPA: High in caudate neuronal projections and intestinal endocrine cells). Treat staining confined to section edges, folds or necrotic areas as suspect, and compare it with intact tissue nearby (standard IHC practice). Check no-primary and detection-only controls for nonspecific color or endogenous enzyme activity (standard IHC practice). HPA describes only medium consistency between antibody staining and RNA expression, so corroborate an unexpected distribution with an independent control (HPA: Enhanced reliability description).

Boster reagents

Best ADORA2A / Adenosine receptor A2a IHC Antibodies

M02268 has real IHC data from human heart paraffin sections (M02268 image caption); the catalog lists no IF/ICC data (catalog: M02268 applications and image records).

Real IHC data

Anti-ADORA2A Antibody (C-term)

Cat # M02268

View product →

M02268 is listed for human IHC-P (catalog: M02268 applications and reactivity). Its figure shows ADORA2A staining in human heart paraffin sections (M02268 image caption).

Which to pick: Choose M02268 for human tissue IHC-P: it is a rabbit polyclonal antibody listed at 1:25, and its figure shows human heart paraffin sections (catalog: M02268 host, clonality, dilution and image caption). The caption reports paraformaldehyde-fixed sections and formaldehyde fixation (M02268 image caption). No listed SKU supports an IF/ICC or cross-species recommendation: M02268 lists human reactivity and no IF/ICC application or figure (catalog: M02268 reactivity, applications and image records).

Each figure is that product's own IHC / IF validation image from its datasheet.

References

UniProt Consortium. UniProt entry P29274 (AA2AR_HUMAN, Adenosine receptor A2a).
Human Protein Atlas. ADORA2A tissue IHC expression (reliability: Enhanced).
Human Protein Atlas. ADORA2A subcellular location (ICC-IF): Mainly localized to the plasma membrane. In addition localized to vesicles and primary cilium..
Human Protein Atlas. ADORA2A antibody validation summary (3 antibodies).
A lncRNA-immune checkpoint-related gene signature predicts metastasis-free survival in prostate adenocarcinoma. Translational andrology and urology 2022 — PMC9827409.
Adenosine A₂A receptors in striatal glutamatergic terminals and GABAergic neurons oppositely modulate psychostimulant action and DARPP-32 phosphorylation. PloS one 2013 — PMC3842921.
Blockade of endothelial adenosine receptor 2 A suppresses atherosclerosis in vivo through inhibiting CREB-ALK5-mediated endothelial to mesenchymal transition. Pharmacological research 2024 — PMC12674621.
Targeting adenosine 2A receptor signaling suppresses vascular calcification by restraining smooth muscle osteogenic differentiation. Pharmacological research 2025 — PMC13331241.
PubMed PMID:1331670 — UniProt-cited evidence.
PubMed PMID:8670304 — UniProt-cited evidence.
PubMed PMID:15461802 — UniProt-cited evidence.