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APOL1 / Apolipoprotein L1 · IHC design guide
Design Immunohistochemistry for APOL1
Plan chromogenic APOL1 IHC on paraffin sections with the IHC-validated antibody at 0.5–1 µg/mL (datasheet A01841-1). Assess plasma staining (HPA tissue IHC) and interpret cellular signal alongside APOL1 secretion (UniProt).
Evidence assembled Oct 2026 · For research use; verify linked source records and product datasheet before use
APOL1 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 | Plasma staining (HPA tissue IHC); secreted (UniProt) | |
| Staining pattern | Distinct positivity in plasma (HPA tissue IHC) | |
| Antigen retrieval | Citrate pH 6 HIER, heat-mediated (datasheet A01841-1) | |
| Positive control | Duodenum+1 more · see all | |
| Negative control | Adipose tissue+4 more · see all |
Important caveats
Reasons your staining may differ from the expected pattern.
| Fixation | Keep fixation consistent across paraffin sections. (standard IHC practice; not target-specific) | |
| Caveat | Secreted APOL1 may contribute to plasma staining (UniProt) | |
| Regulation | Liver-enhanced RNA; staining may differ (HPA tissue RNA + IHC) | |
| Isoform / epitope | 3 isoforms; check epitopes against mature chain 28–398 (UniProt) |
Section 1
Recommended APOL1 IHC & IF Protocols
The catalog antibody’s IHC-P protocol is followed by four published APOL1 chromogenic IHC protocols covering human choroid plexus, arterial sections and mouse tissues (datasheet A01841-1; PMC12236173; PMC11722280; PMC8651054; PMC9591058).
| Sample | Paraffin-embedded human liver cancer tissues; fixative not specified (datasheet A01841-1) |
| Fixation | Image fixative and duration unreported (datasheet A01841-1); verify before use. |
| Sectioning | 4–5 µm sections on charged slides (standard) |
| Deparaffinisation | Xylene, graded ethanol series to water (standard) |
| Antigen retrieval | Heat retrieval: Citrate pH 6, 20 min (datasheet A01841-1) |
| Peroxidase block | 3% H2O2, 10 min, room temperature (standard) |
| Blocking | 10% goat serum (datasheet A01841-1) |
| Primary antibody | Rabbit anti-APOL1, 0.5-1μg/ml (datasheet A01841-1) |
| Primary incubation | Overnight at 4 °C (datasheet A01841-1) |
| Detection | Streptavidin-biotin complex (SABC), DAB chromogen (datasheet A01841-1) |
| Counterstain | Hematoxylin, blue, dehydrate and mount (standard) |
| Expected result | APOL1-positive staining in enterocytes of duodenum (HPA tissue IHC: Medium). HPA tissue profile: Distinct positivity in plasma. No signal in the no-primary control. |
💡Decision noteStart with citrate pH 6 heat retrieval (datasheet A01841-1). Three published protocols also use heated citrate buffer (PMC12236173; PMC11722280; PMC9591058).
Section 2
What Is the Expected APOL1 Staining Pattern?
APOL1 is secreted and has no annotated transmembrane segment (UniProt O14791 topology). In tissue IHC, expect distinct plasma positivity and medium staining in duodenal enterocytes and testicular spermatogonia (HPA tissue IHC). HPA rates the tissue pattern Supported, while warning that secretion complicates agreement between tissue RNA and protein and that presumed off-target binding was disregarded (HPA tissue IHC).
| Distinct plasma staining, with medium staining in duodenal enterocytes or testicular spermatogonia (HPA tissue IHC). | This matches the reported IHC pattern (HPA tissue IHC). Because APOL1 is secreted and occurs in plasma HDL, extracellular signal does not by itself identify the cells that produced it (UniProt O14791 tissue specificity; HPA tissue IHC caveat). |
| Predominantly nuclear staining in an otherwise positive section. | A nuclear pattern does not fit the secreted protein annotation or HPA's membrane/secreted summary (UniProt O14791 subcellular location; HPA subcellular). Treat it as suspect and check a negative reagent control and an independently validated antibody before assigning APOL1 localisation (general IHC practice). |
| Strong cellular staining in adipocytes or bronchial respiratory epithelial cells. | Those cell types were reported as Not detected (HPA tissue IHC). Consider antibody cross-reactivity or endogenous chromogen-generating activity, especially if a negative reagent control also stains (HPA tissue IHC off-target caveat; general chromogenic IHC practice). |
| Broad, poorly defined colour across cells and surrounding tissue. | This is difficult to score against HPA's distinct plasma pattern and specified medium-positive cell populations (HPA tissue IHC). Compare with a negative reagent control, then review blocking, washing and antibody concentration as general IHC background controls (general IHC practice). |
| No staining in duodenal enterocytes, testicular spermatogonia or plasma. | The result conflicts with the reported medium cellular staining and distinct plasma positivity (HPA tissue IHC). First check whether the expected structures are present; then review reagent performance and the detection workflow before calling APOL1 absent (general IHC practice). |
💡Expected APOL1 appearanceA supported positive result shows distinct plasma signal and medium staining in duodenal enterocytes or testicular spermatogonia; dominant nuclear signal or strong staining in HPA Not detected cell types is suspect (HPA tissue IHC; UniProt O14791 subcellular location).
| Secretion and tissue attribution (UniProt O14791; HPA tissue IHC). | APOL1 occurs in plasma on APOA-I-containing HDL, while HPA reports distinct plasma positivity (UniProt O14791 tissue specificity; HPA tissue IHC). A positive extracellular compartment cannot establish local synthesis; HPA explicitly cautions that tissue RNA and protein locations may differ (HPA tissue IHC). |
| Cell-specific reference pattern (HPA tissue IHC). | Enterocytes and spermatogonia are Medium; adipocytes and bronchial respiratory epithelial cells are Not detected (HPA tissue IHC). Use the named cell populations when judging a slide, rather than treating every cell in a named tissue as an expected positive (HPA tissue IHC). |
| Antibody validation and apparent off-target signal (HPA antibodies; HPA tissue IHC). | Two listed antibodies have Supported IHC status, and HPA says presumed off-target binding was observed and disregarded (HPA antibodies; HPA tissue IHC). Supported is a useful comparison point, but an unexpected compartment or cell population still needs a specificity check (general IHC practice). |
| Processing and sequence variation (UniProt O14791). | The annotated signal peptide spans residues 1–27, the mature chain spans 28–398, and three isoforms are listed (UniProt O14791 processing; isoforms). Epitope coverage cannot be inferred without the antibody's immunogen or epitope information (general antibody interpretation practice). |
| Limits of IF localisation evidence (HPA subcellular). | HPA summarizes APOL1 as Membrane, Secreted, but supplies no main location or ICC-IF image-bearing cell line (HPA subcellular). Treat a precise IF compartment assignment as provisional; UniProt also annotates APOL1 as secreted with no transmembrane segment (UniProt O14791 topology). |
| Situation | Likely cause | Next action |
|---|---|---|
| No signal in a section expected to contain positive cells. | The expected cells may be absent, or an IHC reagent or detection step may have failed (HPA tissue IHC; general IHC practice). | Confirm enterocytes or spermatogonia are present, then check an established positive section and each detection reagent (HPA tissue IHC; general IHC practice). |
| Plasma stains, but the intended cellular population does not. | Plasma APOL1 can be present independently of detectable local cellular staining (UniProt O14791 tissue specificity; HPA tissue IHC caveat). | Score plasma and cells separately; verify the sampled cells against HPA's Medium enterocyte or spermatogonia observations (HPA tissue IHC). |
| Strong signal appears in an HPA Not detected cell type. | Possible off-target binding or endogenous detection activity; HPA reports presumed off-target binding in its tissue assessment (HPA tissue IHC; general chromogenic IHC practice). | Run a negative reagent control and compare with an independently validated antibody; review endogenous activity blocking if the control stains (general IHC practice). |
| The whole section has diffuse chromogenic background. | Nonspecific reagent binding or incomplete washing can obscure the distinct pattern reported by HPA (general IHC practice; HPA tissue IHC). | Inspect the negative reagent control, then review blocking, washes and antibody concentration using the assay's validated instructions (general IHC practice). |
| Signal is mainly nuclear. | That compartment lacks support in the supplied APOL1 localisation records (UniProt O14791 subcellular location; HPA subcellular). | Check controls and compare another Supported IHC antibody before interpreting nuclear colour as APOL1 (HPA antibodies; general IHC practice). |
| What should an IF/ICC signal mean? | HPA lists Membrane, Secreted but gives no main subcellular location or ICC-IF image-bearing cell line (HPA subcellular). | Describe the observed IF compartment cautiously and confirm specificity with controls; do not treat membrane-only fluorescence as an established APOL1 reference pattern (HPA subcellular; general IF practice). |
Experiment evidence
IHC & IF images showing APOL1 staining
A01841-1 · IHCIHC analysis of APOL1 using anti-APOL1 antibody (A01841-1). APOL1 was detected in paraffin-embedded section of human liver cancer tissues. H
A01841-1 · IHCIHC analysis of APOL1 using anti-APOL1 antibody (A01841-1). APOL1 was detected in paraffin-embedded section of human liver cancer tissues. H
A01841-2 · IHCAPOL1 Antibody IHC analysis in formalin fixed and paraffin embedded human breast carcinoma followed by peroxidase conjugation of the seconda
HPA · Cerebral cortexHuman Protein Atlas IHC, Cerebral cortex. Source: https://www.proteinatlas.org/ENSG00000100342-APOL1/tissue/cerebral+cortex#imid_14928760
HPA · ColonHuman Protein Atlas IHC, Colon. Source: https://www.proteinatlas.org/ENSG00000100342-APOL1/tissue/colon#imid_14928678
HPA · LiverHuman Protein Atlas IHC, Liver. Source: https://www.proteinatlas.org/ENSG00000100342-APOL1/tissue/liver#imid_14928695
HPA · KidneyHuman Protein Atlas IHC, Kidney. Source: https://www.proteinatlas.org/ENSG00000100342-APOL1/tissue/kidney#imid_14928688
← swipe / scroll for more images →
Real IHC / IF data behind the staining-pattern expectations in this section.
Sample controls for APOL1 IHC & IF
🧪Run duodenum first: enterocytes should stain for APOL1 (HPA: Medium in duodenal enterocytes). Use adipose tissue as the negative comparator, focusing on adipocytes (HPA: Not detected in adipocytes); on the duodenum slide, treat staining outside enterocytes as background only after checking it against the control slides, since the supplied HPA rows do not establish another negative cell type there.
Positive control tissue: Duodenum (Enterocytes, HPA Medium)
Negative control tissue: Adipose tissue (HPA Not detected)
ICC-IF cell lines (HPA subcellular resource): HPA carries no ICC-IF cell line for APOL1; derive a cell-line control from the positive tissue's cell type (Enterocytes) and confirm it by RNA or western blot first.
Technical controls: Include a no-primary, secondary-only control and a rabbit IgG isotype control matched to the primary antibody’s clonality where applicable (caption: rabbit anti-APOL1 primary); an APOL1 knockout specimen, if available, provides a biological negative. Quench endogenous peroxidase and check for endogenous biotin signal in duodenum before interpreting the biotin-based SABC–DAB result (caption: biotinylated secondary and SABC–DAB detection).
⚠️Feasibility: A target-specific fixation window or fixation effect is unreported in the supplied evidence, and the selected A01841-1 tissue-IHC caption does not state the fixative. That caption reports citrate retrieval at pH 6 for 20 minutes in a paraffin section, but does not establish whether retrieval is required; the evidence also does not establish that frozen sections or IF would be easier. In duodenum, assess possible endogenous biotin signal with the planned detection system, and interpret extracellular staining cautiously because APOL1 is secreted (UniProt O14791 subcellular; caption: SABC–DAB detection).
HPA tissue IHC evidence for APOL1
Comprehensive Human Protein Atlas IHC scoring per tissue (reliability: Supported — At least one protein variant secreted, tissue location of RNA and protein might differ and correlation is complex. 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 |
|---|---|---|---|---|
| Duodenum | Enterocytes | Medium | Protein (IHC) | HPA → |
| Testis | Spermatogonia cells | Medium | Protein (IHC) | HPA → |
Undetected expression · recommended negative controls
| Tissue | Cell type | Level | Evidence | Source |
|---|---|---|---|---|
| Adipose tissue | Adipocytes | Not detected | Protein (IHC) | HPA → |
| Adrenal gland | Glandular cells | Not detected | Protein (IHC) | HPA → |
| Appendix | Endocrine cells | Not detected | Protein (IHC) | HPA → |
| Bone marrow | Hematopoietic cells | Not detected | Protein (IHC) | HPA → |
| Breast | Adipocytes | Not detected | Protein (IHC) | HPA → |
Section 3
Advanced APOL1 IHC Tips
Troubleshoot APOL1 staining in paraffin sections by checking retrieval, detection, and compartment-specific controls before scoring chromogenic signal.
How should I troubleshoot weak APOL1 staining after antigen retrieval?
Start with heat-mediated citrate retrieval at pH 6 for 20 minutes on paraffin sections (datasheet A01841-1). Compare adjacent sections processed with and without primary antibody to separate retrieval failure from detection background (standard IHC practice). Keep section thickness, heating, and cooling consistent while assessing retrieval changes (standard IHC practice). If staining remains weak, extend citrate exposure incrementally on adjacent sections and inspect for tissue damage or rising background (standard IHC practice). Assess plasma separately from cellular staining because APOL1 is secreted and HPA reports distinct plasma positivity (UniProt O14791: secreted; HPA: distinct positivity in plasma).
Can fixation explain inconsistent APOL1 staining between paraffin sections?
The selected paraffin-section caption does not state a fixative, so APOL1-specific sensitivity to fixation is unknown (A01841-1 tissue-IHC caption: fixative not stated). Record each specimen's fixative and fixation duration before comparing staining intensity across cases (standard IHC practice). Process adjacent sections together using citrate pH 6 retrieval for 20 minutes as the documented starting condition (datasheet A01841-1). Include a no-primary control and inspect tissue preservation before changing antibody concentration (standard IHC practice). Differences that track processing batches warrant controlled fixation and retrieval comparisons; they do not establish a specific APOL1 fixation effect (standard IHC practice).
Where should APOL1 signal appear, and when is cellular staining credible?
Expect extracellular or plasma-associated signal because APOL1 is secreted, associates with HDL3, and shows distinct plasma positivity in tissue IHC (UniProt O14791: secreted, HDL3; HPA: distinct positivity in plasma). APOL1 has no annotated transmembrane segment, so a crisp membrane rim alone should prompt closer validation (UniProt O14791 topology). Compare cellular staining with local plasma signal and a no-primary control on adjacent sections (standard IHC practice). HPA reports medium staining in duodenal enterocytes and testicular spermatogonia, providing comparison patterns rather than universal cellular expectations (HPA tissue IHC). Document whether DAB is extracellular, cytoplasmic, or membrane-associated before assigning a positive cell population (standard IHC practice).
Could APOL1 isoforms or epitope processing alter the IHC pattern?
APOL1 has 3 annotated isoforms and a signal peptide at residues 1–27, followed by the mature chain at 28–398 (UniProt O14791). Confirm which sequence the catalog antibody recognizes before treating unequal staining as isoform-specific expression (standard IHC practice; UniProt O14791: isoforms 1–3). The supplied caption establishes staining conditions but does not identify the antibody epitope (A01841-1 tissue-IHC caption). Glycosylation at residue 261 and phosphorylation at 311 and 314 are annotated; their effects on this antibody's IHC binding are unknown (UniProt O14791 modifications). Use independent antibody validation or an orthogonal assay when an epitope-dependent interpretation matters (standard IHC practice).
How can IF help resolve ambiguous APOL1 IHC staining?
Use IF as a separate validation experiment and retain chromogenic IHC as the primary readout for this page (A01841-1 tissue-IHC caption). Multiplex APOL1 with a marker for the suspected cell population; choose the marker after examining the section rather than assuming plasma-associated signal is intracellular (HPA: distinct plasma positivity; standard IF practice). Select fluorophores in channels with low tissue autofluorescence and include single-stain and no-primary controls (standard IF practice). Set permeabilisation according to whether the tested epitope is accessible extracellularly or requires intracellular access; the supplied caption does not map that epitope (A01841-1 tissue-IHC caption; standard IF practice). Compare cell boundaries and extracellular spaces before translating IF localisation into an IHC scoring rule (standard IF and IHC practice).
What should I check when APOL1 DAB staining is diffuse or widespread?
First compare the stained section with a no-primary control and inspect the distribution of precipitate across tissue and slide edges (standard IHC practice). The selected workflow used 10% goat serum, biotinylated secondary antibody, streptavidin-biotin detection, and DAB (A01841-1 tissue-IHC caption). Check endogenous peroxidase blocking and, where relevant, endogenous biotin when background follows tissue structures independently of primary antibody (standard IHC practice). APOL1's secreted, plasma-associated distribution can also produce genuine extracellular signal, so diffuse staining alone does not prove nonspecific binding (UniProt O14791: secreted, HDL3; HPA: distinct plasma positivity). HPA reports presumed off-target binding in its tissue assessment, supporting cautious review of unexpected patterns (HPA tissue IHC: reliability description).
How should I quantify APOL1 when plasma and cells both stain? ⚠ ANSWER MARKED FOR VERIFICATION
Define separate extracellular and cellular regions before scoring because APOL1 is secreted and HPA reports distinct plasma positivity (UniProt O14791: secreted; HPA: distinct positivity in plasma). For a specified cell population, record percent positive cells and intensity grades 0–3, then calculate an H-score on the 0–300 scale (standard IHC scoring practice). For extracellular staining, measure DAB-positive area or optical density per mm² of viable tissue (standard image-analysis practice). Apply the same threshold, counterstain settings, and exclusion criteria to every section (standard IHC quantification practice). Report cellular values per eligible cells and extracellular values per viable area, excluding necrosis and damaged edges (standard IHC quantification practice).
How can I distinguish credible APOL1 positivity from staining artefact?
Judge each positive pattern against APOL1's secreted, HDL-associated biology and HPA's distinct plasma positivity (UniProt O14791: secreted, HDL3; HPA: distinct positivity in plasma). A strong cellular or membrane-restricted pattern needs independent support because APOL1 has no annotated transmembrane segment and HPA notes presumed off-target binding (UniProt O14791 topology; HPA tissue IHC: reliability description). Compare the suspected cells with a no-primary control and with extracellular staining in the same section (standard IHC practice). Exclude signal confined to folded edges, necrotic regions, or endogenous enzyme deposits from positive-cell scoring (standard IHC practice). Report compartment and cell identity alongside intensity so plasma staining is not counted as cellular expression (standard IHC practice; HPA: distinct positivity in plasma).
Boster reagents
Best APOL1 / Apolipoprotein L1 IHC Antibodies
The catalog provides human APOL1 paraffin-section IHC images (catalog image captions) and a human-reactive ICC/IF antibody without an IF image (catalog applications; IF image alts).
Real IHC data
Anti-Apolipoprotein L1/APOL1 Antibody ®
Cat # A01841-1
Real IHC data
Anti-APOL1 Antibody
Cat # A01841-2
A01841-1 has an IHC image from a paraffin-embedded human liver cancer section; its fixative is unreported (A01841-1 image caption). A01841-2 has an IHC image from formalin-fixed, paraffin-embedded human breast carcinoma (A01841-2 image caption).
Which to pick: For tissue IHC, choose A01841-1 for the documented paraffin-section preparation (A01841-1 image caption) or A01841-2 for the documented paraffin-section, paraffin-embedded preparation (A01841-2 image caption). For IF/ICC, M01841-1 is a human-reactive rabbit monoclonal, clone 19A39, with ICC/IF listed but no IF image supplied (M01841-1 catalog reactivity, host, clone, applications, IF image alts). None is documented for another species; all three list human reactivity only (catalog reactivity). The selected A01841-1 tissue-IHC caption documents paraffin sections, but does not specify the fixative (selected-SKU IHC image A01841-1).
Each figure is that product's own IHC / IF validation image from its datasheet.
References
- UniProt Consortium. UniProt entry O14791 (APOL1_HUMAN, Apolipoprotein L1).
- Human Protein Atlas. APOL1 tissue IHC expression (reliability: Supported).
- Human Protein Atlas. APOL1 subcellular location (ICC-IF): Membrane, Secreted.
- Human Protein Atlas. APOL1 antibody validation summary (2 antibodies).
- Apolipoprotein-L1 G1 variant contributes to hydrocephalus but not to atherosclerosis in apolipoprotein-E knock-out mice. Clinical science (London, England : 1979) 2025 — PMC12236173.
- Apolipoprotein-L1 G1 variant contributes to hydrocephalus but not to atherosclerosis in apolipoprotein-E knock-out mice. bioRxiv : the preprint server for biology 2024 — PMC11722280.
- APOL1 Genetic Variants Are Associated With Increased Risk of Coronary Atherosclerotic Plaque Rupture in the Black Population. Arteriosclerosis, thrombosis, and vascular biology 2021 — PMC8651054.
- Variant APOL1 protein in plasma associates with larger particles in humans and mouse models of kidney injury. PloS one 2022 — PMC9591058.
- PubMed PMID:9325276 — UniProt-cited evidence.
- PubMed PMID:11290834 — UniProt-cited evidence.
- PubMed PMID:11374903 — UniProt-cited evidence.
Immunohistochemistry protocol sheet for APOL1 (Apolipoprotein L1). Expected localisation Plasma staining (HPA tissue IHC); secreted (UniProt). Antigen retrieval: Citrate pH 6 HIER, heat-mediated (datasheet A01841-1). Validated IHC antibody: A01841-1 at 0.5-1μg/ml (the product's own IHC validation image is shown). Controls (HPA): positive Duodenum (Enterocytes); negative Adipose tissue. IHC-P workflow on paraffin sections; fixative unspecified. Protocol steps: 1. Sample: Paraffin-embedded human liver cancer tissues; fixative not specified (datasheet A01841-1); 2. Fixation: Image fixative and duration unreported (datasheet A01841-1); 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: Citrate pH 6 , 20 min (datasheet A01841-1); 6. Peroxidase block: 3% H2O2, 10 min , room temperature (standard); 7. Blocking: 10% goat serum (datasheet A01841-1); 8. Primary antibody: Rabbit anti-APOL1, 0.5-1μg/ml (datasheet A01841-1); 9. Primary incubation: Overnight at 4 °C (datasheet A01841-1). Watch for: Fixation: Keep fixation consistent across paraffin sections. (standard IHC practice; not target-specific); Caveat: Secreted APOL1 may contribute to plasma staining (UniProt); Isoform / epitope: 3 isoforms; check epitopes against mature chain 28–398 (UniProt); Regulation: Liver-enhanced RNA; staining may differ (HPA tissue RNA + IHC). Evidence: UniProt O14791, HPA tissue IHC · Supported, HPA ICC-IF · Membrane, Secreted, Datasheet A01841-1, PMC12236173, PMC11722280. QR code links to https://www.bosterbio.com/bosterbio-gene-info-cards/APOL1/immunohistochemistry-ihc-guide.