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ERAP1 / Endoplasmic reticulum aminopeptidase 1 · IHC design guide
Design Immunohistochemistry for ERAP1
Plan ERAP1 chromogenic IHC using the cytoplasmic tissue pattern reported by HPA and its ER membrane location annotated by UniProt. Compare staining with HPA high expressing cells, including kidney tubule cells and hepatocytes, while keeping fixation consistent across sections.
Evidence assembled Oct 2026 · For research use; verify linked source records and product datasheet before use
ERAP1 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 tissue staining (HPA tissue IHC); ER membrane (UniProt) | |
| Staining pattern | General cytoplasmic staining in several tissues (HPA tissue IHC) | |
| Antigen retrieval | Citrate pH 6.0 HIER, 95–98 °C, 20 min (rule: cytoplasmic / membrane antigen) | |
| Positive control | Adipose tissue+4 more · see all | |
| Negative control | None in HPA (detected in all 45 tissues); use no-primary + isotype controls |
Important caveats
Reasons your staining may differ from the expected pattern.
| Fixation | Keep fixation consistent across sections (standard IHC practice; not target-specific) | |
| Caveat | A secreted variant may alter tissue staining (HPA tissue IHC) | |
| Regulation | No specific expression regulator reported (UniProt) | |
| Isoform / epitope | 2 isoforms; epitope differences unreported; mostly luminal (UniProt) |
Section 1
Recommended ERAP1 IHC & IF Protocols
The catalog antibody protocol is accompanied by published paraffin section IHC protocols for placental tissue and classical Hodgkin lymphoma (PMC7076169; PMC7865538).
| Sample | Tissue sections; selected-image fixative not specified (standard IHC workflow) |
| Fixation | Image fixative and duration unreported (datasheet A02021-1); 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-ERAP1, 1:100–1:500 starting range (standard) |
| 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 | ERAP1-positive staining in adipocytes of adipose tissue (HPA tissue IHC: High). HPA tissue profile: General cytoplasmic expression in several tissues. No signal in the no-primary control. |
💡Decision noteStart with citrate pH 6.0 retrieval for the catalog antibody (page retrieval); EDTA pH 8.0 is a published alternative for lymphoma sections (PMC7865538 methods).
Section 2
What Is the Expected ERAP1 Staining Pattern?
In paraffin IHC, expect chiefly cytoplasmic ERAP1 staining in several tissues, including kidney tubule cells, hepatocytes, adipocytes and selected glandular cells (HPA tissue IHC: Approved; High in these cells). UniProt places ERAP1 at the endoplasmic reticulum membrane, with residues 22–941 lumenal (UniProt Q9NZ08: topology). HPA rates its tissue IHC profile Approved but reports only medium consistency with RNA expression (HPA tissue IHC: reliability description).
| Cytoplasmic chromogen is strongest in kidney tubule cells, hepatocytes or the listed glandular cells. | This fits HPA's general cytoplasmic profile and its High ratings in those cells (HPA tissue IHC: profile; High in kidney, liver, colon, duodenum, fallopian tube and gallbladder). Compare cell types within the section; a High rating does not prescribe identical intensity in every specimen (standard IHC interpretation). |
| Strong, isolated nuclear or sharply cell-surface staining dominates the paraffin section. | Treat this as a compartment mismatch with HPA's tissue IHC profile and investigate specificity and detection artefact (HPA tissue IHC: general cytoplasmic expression; standard IHC practice). HPA separately reports approved nucleoplasm, cytosol and additional plasma-membrane locations by ICC-IF; those observations do not establish the dominant paraffin IHC pattern (HPA subcellular: approved locations). |
| A low-rated cell population stains more strongly than nearby High-rated cells. | Check cell identity and specificity before calling it ERAP1 enrichment (HPA tissue IHC: Low in salivary glandular cells, vaginal squamous cells, smooth muscle cells and skeletal myocytes; High in listed positive cells). Cross-reactivity or endogenous chromogenic activity can mimic staining (standard IHC practice); HPA's Low rating is not an absence claim. |
| Chromogen spreads across tissue, blank areas or many cell types without a readable cytoplasmic pattern. | This is background until controls support a cellular signal (standard IHC practice). Review the detection-only control and section edges, then assess blocking, washing and detection conditions (standard IHC practice). HPA's Approved tissue rating does not validate background in a particular run (HPA tissue IHC: Approved). |
| No signal appears in a known High-rated positive tissue. | First assess section quality, control performance, retrieval and antibody detection in that run (standard IHC practice). A blank kidney tubule, hepatocyte or other listed High-rated population conflicts with the HPA reference pattern, but one failed stain cannot establish biological absence (HPA tissue IHC: High in kidney tubules and hepatocytes; standard IHC interpretation). |
💡Expected ERAP1 appearanceCall a result positive when identifiable High-rated cells show readable, predominantly cytoplasmic staining, especially kidney tubule cells or hepatocytes; isolated dominant nuclear staining or diffuse chromogen without cell boundaries is suspect (HPA tissue IHC: profile; High in kidney and liver; standard IHC interpretation).
| Cell-type reference | Use HPA's High-rated populations as positive references and its Low-rated populations as intensity comparators, not proven negatives (HPA tissue IHC: High and Low lists). ERAP1 is described as ubiquitous, so a strict tissue-negative prediction is unsupported (UniProt Q9NZ08: tissue specificity). |
| Topology and compartment | ERAP1 has one membrane segment at residues 2–21 and a lumenal region at 22–941 (UniProt Q9NZ08: topology). This supports an ER-associated interpretation, while HPA describes the visible paraffin IHC profile broadly as cytoplasmic (HPA tissue IHC: profile). |
| Protein forms and assay limits | UniProt lists 2 isoforms and 5 glycosylation sites (UniProt Q9NZ08: isoforms; glycosylation). The supplied evidence gives no antibody epitope or isoform coverage, so it cannot predict which forms a particular IHC stain detects (UniProt Q9NZ08: record; HPA antibodies: validation summary). |
| Tissue-profile reliability | HPA calls tissue IHC Approved while noting medium agreement with RNA and that at least one variant is secreted; RNA and protein locations may differ (HPA tissue IHC: reliability description). Judge the stained cells and compartment directly instead of treating RNA abundance as a slide-level intensity rule (standard IHC interpretation). |
| IF/ICC Q&A: Should IF match the paraffin IHC pattern? | ICC-IF reports approved nucleoplasm and cytosol locations, plus an additional plasma-membrane location, in its own assay (HPA subcellular: approved locations). Interpret those results in the separate IF/ICC context; the tissue IHC reference remains general cytoplasmic expression (HPA tissue IHC: profile). |
| Situation | Likely cause | Next action |
|---|---|---|
| A High-rated control tissue is blank. | The run may have inadequate retrieval, antibody detection or chromogen development (standard IHC practice); the blank result disagrees with the HPA reference (HPA tissue IHC: High list). | Check a matched positive section and detection controls, then optimize the IHC workflow using the antibody's validated instructions (standard IHC practice). No ERAP1-specific retrieval condition is supplied (HPA tissue IHC: supplied record). |
| Signal is mainly nuclear in paraffin IHC. | It differs from the general cytoplasmic tissue pattern, although nuclear localization is reported separately by ICC-IF (HPA tissue IHC: profile; HPA subcellular: nucleoplasm approved). | Check whether cytoplasmic staining is also present in High-rated cells, review controls and confirm the pattern with an independent specificity check before scoring it as expected tissue IHC (standard IHC practice). |
| Smooth muscle or skeletal myocytes dominate the stain. | Both are Low-rated HPA populations; strong staining there raises a cell-identification, specificity or background question (HPA tissue IHC: Low in smooth muscle and skeletal muscle; standard IHC interpretation). | Compare with adjacent High-rated cells where available and inspect detection-only controls; do not label Low-rated cells definitively negative (HPA tissue IHC: High and Low lists; standard IHC practice). |
| Brown signal appears in the detection-only control. | Endogenous enzyme activity or nonspecific detection can create chromogen without primary antibody (standard chromogenic IHC practice). | Address the relevant endogenous activity and detection background, repeat the control, and score ERAP1 only when the primary-dependent cellular pattern is clear (standard chromogenic IHC practice). |
| All cells and extracellular spaces look diffusely stained. | Nonspecific background can obscure the cell-resolved cytoplasmic profile (standard IHC practice; HPA tissue IHC: general cytoplasmic expression). | Review blocking, washing, section edges and chromogen development alongside controls; reassess cell-type intensity only after the background is resolved (standard IHC practice). |
| RNA abundance and tissue staining seem discordant. | HPA reports medium RNA–antibody consistency and warns that a secreted variant can make RNA and protein locations differ (HPA tissue IHC: reliability description). | Record the observed stained cell type and compartment, compare with HPA's IHC profile, and avoid inferring a failed stain from RNA alone (HPA tissue IHC: profile and reliability description; standard IHC interpretation). |
Experiment evidence
IHC & IF images showing ERAP1 staining
A02021-1 · IHCImmunohistochemistry of ERAP1 in mouse brain tissue with ERAP1 antibody at 5 μg/mL.
A02021-1 · IFImmunofluorescence of ERAP1 in mouse brain tissue with ERAP1 antibody at 20 μg/mL.
HPA · Cerebral cortexHuman Protein Atlas IHC, Cerebral cortex. Source: https://www.proteinatlas.org/ENSG00000164307-ERAP1/tissue/cerebral+cortex#imid_6635240
HPA · ColonHuman Protein Atlas IHC, Colon. Source: https://www.proteinatlas.org/ENSG00000164307-ERAP1/tissue/colon#imid_6632862
HPA · LiverHuman Protein Atlas IHC, Liver. Source: https://www.proteinatlas.org/ENSG00000164307-ERAP1/tissue/liver#imid_6632855
HPA · KidneyHuman Protein Atlas IHC, Kidney. Source: https://www.proteinatlas.org/ENSG00000164307-ERAP1/tissue/kidney#imid_6632856
HPA · ICC-IF A-431Human Protein Atlas immunofluorescence, A-431, antibody HPA042317; green = ERAP1, blue = nucleus, red = microtubules.
HPA · ICC-IF A-431Human Protein Atlas immunofluorescence, A-431, antibody HPA042317; green = ERAP1, blue = nucleus, red = microtubules.
← swipe / scroll for more images →
Real IHC / IF data behind the staining-pattern expectations in this section.
Sample controls for ERAP1 IHC & IF
🧪Run colon first: its glandular cells should stain (HPA: High in colon glandular cells). HPA detects ERAP1 in all 45 scored tissues, so there is no supported negative tissue; use no-primary and isotype controls, and assess any unstained cells on the positive slide against the counterstain without assuming a particular cell type is ERAP1-negative (HPA: no negative tissue rows).
Positive control tissue: Adipose tissue (Adipocytes, HPA High)
Negative control tissue: None in HPA: ERAP1 is detected in all 45 scored tissues. Use a no-primary (secondary-only) and an isotype control instead.
ICC-IF cell lines (HPA subcellular resource): HPA ICC-IF images show ERAP1 in A-431, U-251MG, U2OS, NIH 3T3, with annotated localisation: Nucleoplasm (approved), Cytosol (approved) (HPA subcellular).
Technical controls: Include a no-primary, secondary-only slide and an irrelevant immunoglobulin isotype control matched to the primary antibody’s host species and clonality; use ERAP1-knockout material as a biological negative, or peptide competition if the immunizing peptide is available. For chromogenic colon IHC, quench endogenous peroxidase and check inflammatory cells for residual background (standard IHC practice).
⚠️Feasibility: No target-specific fixation window, fixation effect, or retrieval dependency is reported in the supplied evidence; the selected A02021-1 mouse-brain IHC caption reports 5 µg/mL but leaves the fixative unstated (catalog antibody caption). Whether frozen sections or IF are easier is unreported, so optimize retrieval empirically for paraffin IHC; in colon, residual endogenous peroxidase in inflammatory cells can complicate interpretation (standard IHC practice).
HPA tissue IHC evidence for ERAP1
Comprehensive Human Protein Atlas IHC scoring per tissue (reliability: Approved — Medium consistency between antibody staining and RNA expression data. At least one protein variant secreted, tissue location of RNA and protein might differ and correlation is complex.). 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 |
|---|---|---|---|---|
| Adipose tissue | Adipocytes | High | Protein (IHC) | HPA → |
| Colon | Glandular cells | High | Protein (IHC) | HPA → |
| Duodenum | Glandular cells | High | Protein (IHC) | HPA → |
| Fallopian tube | Glandular cells | High | Protein (IHC) | HPA → |
| Gallbladder | Glandular cells | High | Protein (IHC) | HPA → |
Undetected expression · recommended negative controls
| Tissue | Cell type | Level | Evidence | Source |
|---|---|---|---|---|
| None in HPA: ERAP1 is detected in all 45 scored tissues. Use a no-primary (secondary-only) and an isotype control instead. | ||||
Section 3
Advanced ERAP1 IHC Tips
Troubleshoot ERAP1 staining in paraffin sections by checking retrieval, compartment patterns, controls and cell level scoring before interpreting chromogenic signal.
How should I retrieve ERAP1 in paraffin sections when staining is weak?
Start with citrate buffer at pH 6.0, heated to 95–98 °C for 20 min (page retrieval rule). Let sections cool in the retrieval buffer, then compare staining with a matched section processed in the same run (standard IHC practice). If signal remains weak, adjust heating time incrementally while watching for tissue damage; keep the antibody concentration and detection conditions fixed during that comparison (standard IHC practice). ERAP1 has a lumenal region spanning residues 22–941, so antibody access after processing may depend on epitope exposure (UniProt Q9NZ08 topology). Record the retrieval conditions used for every scored slide (standard IHC practice).
Could fixation explain weak or uneven ERAP1 staining?
Target-specific fixation sensitivity is unknown: the selected mouse brain IHC caption gives an antibody concentration of 5 µg/mL but does not state the fixative (caption A02021-1). Do not infer fixation tolerance from tissue staining patterns or ERAP1 topology (HPA tissue IHC; UniProt Q9NZ08 topology). Check section thickness, fixation history where available, and whether weak areas coincide with poor tissue preservation (standard IHC practice). Compare a consistently processed control tissue across staining runs before changing retrieval or antibody concentration (standard IHC practice). If processing histories differ, report them alongside staining scores because fixation differences can affect antigen accessibility in paraffin sections (standard IHC practice).
What cellular pattern should count as plausible ERAP1 staining?
For chromogenic IHC, assess cytoplasmic signal within identifiable cells and document any membrane or nuclear staining separately (HPA tissue IHC; HPA subcellular). UniProt places ERAP1 at the endoplasmic reticulum membrane, with residues 22–941 facing the lumen (UniProt Q9NZ08 topology). HPA tissue IHC describes general cytoplasmic expression, while its cell imaging reports approved nucleoplasmic and cytosolic locations plus an additional plasma membrane location (HPA tissue IHC; HPA subcellular). These sources support recording compartments rather than assuming that every brown deposit represents the same pool of ERAP1. Review staining at cell level with a counterstain, especially where adjacent cell types differ (standard IHC practice).
How do isoforms and epitope location affect ERAP1 IHC interpretation?
ERAP1 has 2 annotated isoforms, but the supplied evidence does not map this antibody’s epitope to either one (UniProt Q9NZ08 isoforms; caption A02021-1). Accordingly, a positive chromogenic result cannot establish which isoform is present without additional epitope or isoform evidence. The protein has a membrane segment at residues 2–21 and a lumenal region at 22–941 (UniProt Q9NZ08 topology). Five glycosylation sites are annotated at residues 70, 154, 414, 760 and 901; their effect on this antibody’s staining is unknown (UniProt Q9NZ08 glycosylation). Ask for the immunogen or epitope coordinates before drawing conclusions about variant-specific staining or access after retrieval.
How should I assess ERAP1 localisation by multiplex IF?
For the separate IF/ICC application, pair ERAP1 with a marker identifying the cell population being assessed; HPA reports high tissue IHC staining in adipocytes and kidney tubule cells, among others (HPA tissue IHC). Choose spectrally separated fluorophores and place the weaker signal in a channel with less tissue autofluorescence, checking single-stain controls for bleed-through (standard IF practice). ERAP1’s major region faces the endoplasmic reticulum lumen beyond residue 21, so an antibody against that region requires access across cellular membranes (UniProt Q9NZ08 topology). Optimise permeabilisation against morphology and background using the antibody’s known epitope, if available (standard IF practice). Keep IF compartment observations distinct from chromogenic IHC scores (HPA subcellular; HPA tissue IHC).
How can I distinguish ERAP1 signal from chromogenic background?
Run a no-primary control through the same peroxidase detection and DAB steps to identify staining unrelated to primary antibody binding (standard IHC practice). Include a peroxidase block, then inspect erythrocyte-rich or damaged regions for residual endogenous enzyme signal (standard IHC practice). If staining becomes diffuse across all tissue structures, compare antibody concentration, wash conditions and retrieval against a matched control section before changing several variables (standard IHC practice). The selected mouse brain caption reports 5 µg/mL for antibody A02021-1, but supplies no fixative information (caption A02021-1). Score signal within preserved cells rather than counting deposits at folds, section edges or necrotic areas (standard IHC practice).
What is a defensible way to quantify ERAP1 IHC across samples? ⚠ ANSWER MARKED FOR VERIFICATION
Define the cell population and compartment before scoring, because HPA tissue IHC reports general cytoplasmic staining across several tissues (HPA tissue IHC). For a cell level comparison, record the percentage of positive cells and intensity categories, then calculate an H-score on the 0–300 scale (standard IHC practice). If cell boundaries cannot be resolved reliably, report positive area or cell density per mm² within a defined region instead (standard IHC practice). Normalise to the number of eligible cells or analyzable tissue area, and exclude folds, necrosis and empty space (standard IHC practice). Use the same retrieval, imaging and scoring thresholds across compared sections (standard IHC practice).
When does an ERAP1 positive result warrant skepticism?
A convincing result should form a repeatable pattern within intact cells and remain absent from the corresponding no-primary control (standard IHC practice). HPA reports high staining in kidney tubule cells, hepatocytes and lymph node germinal center cells, while smooth muscle and skeletal muscle are listed as low (HPA tissue IHC). Use those differences as context, allowing for the sample’s actual cell composition rather than assigning a single whole-section score. ERAP1 is annotated at the endoplasmic reticulum membrane, while HPA also reports cytosolic, nucleoplasmic and plasma membrane locations (UniProt Q9NZ08 topology; HPA subcellular). Investigate isolated nuclear or extracellular deposits, edge effects, necrosis and residual endogenous peroxidase before calling unexpected staining positive (standard IHC practice).
Boster reagents
Best ERAP1 / Endoplasmic reticulum aminopeptidase 1 IHC Antibodies
A02021-1 has mouse-brain IHC and IF images and lists human and mouse reactivity (catalog image captions; catalog reactivity). M02021-1 lists IHC and human, mouse and rat reactivity (catalog applications/reactivity).
Real IHC data
Anti-ERAP1 Antibody
Cat # A02021-1
A02021-1 is the SKU with a rendered card; its IHC image shows mouse brain stained at 5 μg/mL (IHC image caption). Its IF image also shows mouse brain, stained at 20 μg/mL (IF image caption).
Which to pick: For tissue IHC, choose A02021-1 for its IHC-P listing and mouse-brain IHC image; the caption does not report the fixative (catalog applications; IHC image caption). For IF, choose A02021-1 based on its mouse-brain IF image; ICC validation is unreported (IF image caption; catalog applications). If rat reactivity is needed, M02021-1 lists rat and IHC and is rabbit monoclonal, but its payload provides no IHC image or rat IHC validation (catalog reactivity/applications; catalog host/clone; catalog image captions).
Each figure is that product's own IHC / IF validation image from its datasheet.
References
- UniProt Consortium. UniProt entry Q9NZ08 (ERAP1_HUMAN, Endoplasmic reticulum aminopeptidase 1).
- Human Protein Atlas. ERAP1 tissue IHC expression (reliability: Approved).
- Human Protein Atlas. ERAP1 subcellular location (ICC-IF): Mainly localized to the nucleoplasm and cytosol. In addition localized to the plasma membrane..
- Human Protein Atlas. ERAP1 antibody validation summary (2 antibodies).
- The Differential Expression of ERAP1/ERAP2 and Immune Cell Activation in Pre-eclampsia. Frontiers in immunology 2020 — PMC7076169.
- ERAP1 promotes Hedgehog-dependent tumorigenesis by controlling USP47-mediated degradation of βTrCP. Nature communications 2019 — PMC6656771.
- Molecular backgrounds of ERAP1 downregulation in cervical carcinoma. Analytical cellular pathology (Amsterdam) 2015 — PMC4471254.
- Interaction between ERAP Alleles and HLA Class I Types Support a Role of Antigen Presentation in Hodgkin Lymphoma Development. Cancers 2021 — PMC7865538.
- PubMed PMID:10220586 — UniProt-cited evidence.
- PubMed PMID:11481040 — UniProt-cited evidence.
- PubMed PMID:9628581 — UniProt-cited evidence.
Immunohistochemistry protocol sheet for ERAP1 (Endoplasmic reticulum aminopeptidase 1). Expected localisation Cytoplasmic tissue staining (HPA tissue IHC); ER membrane (UniProt). Antigen retrieval: Citrate pH 6.0 HIER, 95–98 °C, 20 min (rule: cytoplasmic / membrane antigen). Validated IHC antibody: A02021-1 at 1:100–1:500 (standard starting range) (the product's own IHC validation image is shown). Controls (HPA): positive Adipose tissue (Adipocytes); negative None in HPA (detected in all 45 tissues); use no-primary + isotype controls. IHC workflow; specimen preparation unspecified. Protocol steps: 1. Sample: Tissue sections; selected-image fixative not specified (standard IHC workflow); 2. Fixation: Image fixative and duration unreported (datasheet A02021-1); 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-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-ERAP1, 1:100–1:500 starting range (standard); 9. Primary incubation: Overnight at 4 °C (standard). Watch for: Fixation: Keep fixation consistent across sections (standard IHC practice; not target-specific); Caveat: A secreted variant may alter tissue staining (HPA tissue IHC); Isoform / epitope: 2 isoforms; epitope differences unreported; mostly luminal (UniProt); Regulation: No specific expression regulator reported (UniProt). Evidence: UniProt Q9NZ08, HPA tissue IHC · Approved, HPA ICC-IF · Mainly localized to the nucleoplasm and cytosol. In addition…, Datasheet A02021-1, PMC7076169, PMC7865538. QR code links to https://www.bosterbio.com/bosterbio-gene-info-cards/ERAP1/immunohistochemistry-ihc-guide.