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CYP11A1 / Cholesterol side-chain cleavage enzyme, mitochondrial · IHC design guide
Design Immunohistochemistry for CYP11A1
Plan CYP11A1 chromogenic IHC in paraffin sections using granular cytoplasmic staining and documented positive cell populations as reference points (HPA tissue IHC). The guide covers fixation, detection and interpretation for a protein located at the matrix side of the mitochondrial inner membrane (UniProt).
Evidence assembled Oct 2026 · For research use; verify linked source records and product datasheet before use
CYP11A1 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 | Granular cytoplasm (HPA tissue IHC); mitochondrial inner membrane, matrix side (UniProt). | |
| Staining pattern | Granular cytoplasm in zona fasciculata, cytotrophoblasts and Leydig cells (HPA tissue IHC). | |
| Antigen retrieval | Citrate pH 6.0 HIER, 95–98 °C, 20 min (rule: cytoplasmic / membrane antigen) | |
| Positive control | Adrenal gland+2 more · see all | |
| Negative control | Adipose tissue+4 more · see all |
Important caveats
Reasons your staining may differ from the expected pattern.
| Fixation | Keep paraffin-section fixation consistent across samples. (standard IHC practice; not target-specific) | |
| Caveat | Expression varies by tissue and cell type (HPA tissue IHC). | |
| Regulation | High in adrenal gland, placenta and testis (HPA tissue IHC). | |
| Isoform / epitope | Two isoforms; whether PA1698 detects both is unknown (UniProt; catalog). |
Section 1
Recommended CYP11A1 IHC & IF Protocols
The catalog antibody’s IHC-P protocol is followed by four published CYP11A1 staining protocols for adrenal or testis sections (PMC11586580; PMC12375238; PMC7541273; PMC8072358).
| Sample | Tissue sections; selected-image fixative not specified (standard IHC workflow) |
| Fixation | Image fixative and duration unreported (datasheet PA1698); 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-CYP11A1, 0.5-1μg/ml (datasheet PA1698) |
| 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 | CYP11A1-positive staining in cells in zona fasciculata of adrenal gland (HPA tissue IHC: High). HPA tissue profile: Granular cytoplasmic expression, most abundant in adrenal gland, placenta and testis. No signal in the no-primary control. |
💡Decision noteStart with citrate pH 6.0 retrieval at 95–98 °C for 20 min (page retrieval rule); compare staining with tissue controls (standard IHC practice).
Section 2
What Is the Expected CYP11A1 Staining Pattern?
In paraffin-section IHC, expect CYP11A1 as granular cytoplasmic staining in adrenal zona fasciculata cells, placental cytotrophoblasts, and testicular Leydig cells (HPA: High in each). The pattern is consistent with localization on the matrix side of the mitochondrial inner membrane; individual membranes need not be resolved by light microscopy (UniProt P05108 topology). HPA rates the tissue staining profile Enhanced, citing consistency with RNA expression (HPA: Enhanced).
| Granular cytoplasmic staining in the expected cells, strongest in an appropriate positive tissue. | This fits the reported tissue pattern and mitochondrial localization (HPA: High in zona fasciculata cells, cytotrophoblasts, and Leydig cells; UniProt P05108 topology). Compare cells within the section: a correct result should preserve recognizable cell-specific staining rather than tint every cell equally (general IHC practice). |
| Predominantly nuclear staining, or a uniform stain unrelated to cytoplasmic granules. | This does not match the expected mitochondrial, granular cytoplasmic pattern (UniProt P05108 topology; HPA: granular cytoplasmic expression). Treat it as suspect and examine antibody specificity, counterstain, and detection controls before interpreting it as CYP11A1 (general IHC practice). |
| Strong staining in a cell type reported as undetected, such as adipocytes or appendix glandular cells. | HPA reports CYP11A1 as Not detected in those cells (HPA: adipocytes and appendix glandular cells). Check morphology and repeat with appropriate controls; cross-reactivity or endogenous chromogenic activity is possible, but an unexpected result alone does not identify its cause (general IHC practice). |
| Pale, diffuse color over cells and surrounding tissue, with little cellular distinction. | Diffuse color lacks the reported granular cytoplasmic distribution (HPA: granular cytoplasmic expression). Assess background with a no-primary control and review blocking, washing, and detection conditions before assigning a positive score (general IHC practice). |
| No staining in a section containing clearly identifiable adrenal zona fasciculata cells. | That conflicts with the reported High staining in these cells (HPA: adrenal zona fasciculata cells, High). Verify tissue identity and assay controls, then review the antibody’s validated IHC-P conditions; this record gives no target-specific fixation or retrieval sensitivity (general IHC practice; HPA: tissue IHC). |
💡Expected CYP11A1 appearanceCall a result positive when distinct High granular cytoplasmic staining occurs in the expected cells (HPA: High; UniProt P05108 topology); uniform nuclear or widespread diffuse color is suspect (general IHC practice).
| Cell type and tissue | Use adrenal zona fasciculata cells, placental cytotrophoblasts, or testicular Leydig cells as expected positives (HPA: High). Adipocytes and appendix glandular cells are reported Not detected, making them useful comparison cells, not absolute proof of specificity (HPA: Not detected; general IHC practice). |
| Subcellular resolution | CYP11A1 lies on the matrix side of the mitochondrial inner membrane, with no annotated transmembrane segment (UniProt P05108 topology). Interpret the HPA granular cytoplasmic pattern at light-microscope resolution; it does not establish that individual mitochondrial membranes can be seen (HPA: granular cytoplasmic expression; general IHC practice). |
| Antibody validation and protein forms | HPA lists antibody HPA016436 as IHC Enhanced (HPA: antibody validation). UniProt lists 2 isoforms and a mature chain spanning residues 40–521 (UniProt P05108 processing). Neither record specifies which form an IHC stain detects, so avoid isoform-specific calls. |
| IF/ICC Q&A: Is an IF localization pattern established here? | No HPA ICC-IF image set or main location is available (HPA: subcellular record). The mitochondrial location is a UniProt annotation (UniProt P05108 topology); this tissue IHC profile does not validate an IF/ICC pattern or provide an IF protocol (HPA: tissue IHC and subcellular records). |
| Situation | Likely cause | Next action |
|---|---|---|
| Known-positive adrenal cells show no chromogenic signal. | Possible assay failure, tissue-identification error, or staining conditions unsuitable for the antibody; HPA reports these cells as High (HPA: adrenal zona fasciculata cells). | Confirm morphology and a working detection control, then check the IHC-validated antibody’s instructions and run the intended positive tissue alongside the sample (general IHC practice). No target-specific fixation effect is established here. |
| Positive tissue shows color, but staining is mainly nuclear. | Nuclear predominance conflicts with mitochondrial localization and the reported granular cytoplasmic profile (UniProt P05108 topology; HPA: granular cytoplasmic expression). | Inspect counterstain and no-primary controls, then reassess antibody specificity and detection background before scoring the section (general IHC practice). |
| Nearly every cell and the extracellular space appear colored. | Diffuse deposition may reflect background or endogenous chromogenic activity; it lacks the reported cell-specific granular pattern (HPA: granular cytoplasmic expression; general IHC practice). | Use a no-primary control, inspect detection and blocking steps, and compare expected positive cells with nearby cells before interpreting signal (general IHC practice). |
| Reported negative cells stain strongly alongside expected positive cells. | Unexpected staining may arise from cross-reactivity or endogenous activity; HPA reports adipocytes and appendix glandular cells as Not detected (HPA: tissue IHC; general IHC practice). | Confirm cell identity, compare a no-primary control, and seek independent antibody or orthogonal evidence before calling the unexpected signal CYP11A1 (general IHC practice). |
| Adrenal, placenta, and testis sections give very different apparent intensity. | HPA reports High staining in specified cell populations, not an identical chromogen intensity across tissues or preparations (HPA: tissue IHC). | Score the identified positive cell population within each section and compare sections stained under matched assay conditions (general IHC practice). |
| An IF image appears to disagree with the IHC slide. | HPA supplies no ICC-IF images or main subcellular location for this target (HPA: subcellular record). | Interpret the IHC slide against HPA’s tissue pattern and UniProt’s mitochondrial annotation; establish any IF-specific conclusion with its own controls (HPA: tissue IHC; UniProt P05108 topology; general IF practice). |
Experiment evidence
IHC & IF images showing CYP11A1 staining
PA1698 · IHCAnti-CYP11A1 antibody, PA1698, IHC(P) IHC(P): Human Placenta Tissue
PA1698 · IHCAnti-CYP11A1 antibody, PA1698, IHC(F) IHC(F): Human Placenta Tissue
HPA · Cerebral cortexHuman Protein Atlas IHC, Cerebral cortex. Source: https://www.proteinatlas.org/ENSG00000140459-CYP11A1/tissue/cerebral+cortex#imid_17602507
HPA · Adrenal glandHuman Protein Atlas IHC, Adrenal gland. Source: https://www.proteinatlas.org/ENSG00000140459-CYP11A1/tissue/adrenal+gland#imid_121
HPA · ColonHuman Protein Atlas IHC, Colon. Source: https://www.proteinatlas.org/ENSG00000140459-CYP11A1/tissue/colon#imid_17602433
HPA · LiverHuman Protein Atlas IHC, Liver. Source: https://www.proteinatlas.org/ENSG00000140459-CYP11A1/tissue/liver#imid_17602434
← swipe / scroll for more images →
Real IHC / IF data behind the staining-pattern expectations in this section.
Sample controls for CYP11A1 IHC & IF
🧪Run testis first: Leydig cells should stain strongly (HPA: High in Leydig cells). Use adipose tissue as the negative tissue (HPA: Not detected in adipocytes); on the testis slide, seminiferous-tubule cells should show only background staining, but treat them as an internal comparator rather than a validated negative population (HPA: High in Leydig cells).
Positive control tissue: Adrenal gland (Cells in zona fasciculata, HPA High)
Negative control tissue: Adipose tissue (HPA Not detected)
ICC-IF cell lines (HPA subcellular resource): HPA carries no ICC-IF cell line for CYP11A1; derive a cell-line control from the positive tissue's cell type (Cells in zona fasciculata) and confirm it by RNA or western blot first.
Technical controls: Include a no-primary, secondary-only control and nonimmune IgG matched to the primary antibody’s host species, isotype and monoclonal or polyclonal format (standard IHC practice). Confirm specificity with a CYP11A1 knockout sample where available or cognate-peptide blocking if the immunogen is available; quench endogenous peroxidase for chromogenic IHC and check testis sections for background signal (standard IHC practice).
⚠️Feasibility: A target-specific fixation window or fixation effect is unreported in the supplied evidence, and the selected PA1698 placenta IHC-P caption does not state its fixative (catalog caption: fixative not stated). Retrieval dependence is also unreported; optimize antigen retrieval on paraffin sections with the IHC-validated antibody rather than assuming a condition from the tissue staining pattern (HPA: High in Leydig cells; standard IHC practice). The supplied evidence does not establish that frozen sections or IF are easier; assess background in the chosen tissue during optimization (standard IHC/IF practice).
HPA tissue IHC evidence for CYP11A1
Comprehensive Human Protein Atlas IHC scoring per tissue (reliability: Enhanced — High 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 |
|---|---|---|---|---|
| Adrenal gland | Cells in zona fasciculata | High | Protein (IHC) | HPA → |
| Placenta | Cytotrophoblasts | High | Protein (IHC) | HPA → |
| Testis | Leydig cells | High | Protein (IHC) | HPA → |
Undetected expression · recommended negative controls
| Tissue | Cell type | Level | Evidence | Source |
|---|---|---|---|---|
| Adipose tissue | Adipocytes | Not detected | Protein (IHC) | HPA → |
| Appendix | Glandular cells | Not detected | Protein (IHC) | HPA → |
| Bone marrow | Hematopoietic cells | Not detected | Protein (IHC) | HPA → |
| Breast | Adipocytes | Not detected | Protein (IHC) | HPA → |
| Bronchus | Respiratory epithelial cells | Not detected | Protein (IHC) | HPA → |
Section 3
Advanced CYP11A1 IHC Tips
Troubleshoot CYP11A1 staining in paraffin section IHC by checking retrieval, compartment, cell identity and controls before comparing signal intensity.
How should I retrieve CYP11A1 in paraffin sections when staining is weak?
Start with citrate buffer at pH 6.0, heated to 95–98 °C for 20 minutes (page retrieval rule). Let sections cool in buffer, then compare the same staining run with a no-primary control and a known positive section; adrenal zona fasciculata cells, placental cytotrophoblasts and testicular Leydig cells are documented positive populations (standard IHC practice; HPA tissue IHC). If signal remains weak, test a more intensive retrieval condition on adjacent sections while keeping antibody concentration and detection constant (standard IHC practice). Judge improvement by stronger granular cytoplasmic staining in expected cells without increased staining in HPA-negative cell populations (HPA tissue IHC; standard IHC practice).
Could fixation explain weak CYP11A1 staining in my paraffin sections?
Target-specific fixation sensitivity is unknown from the supplied evidence; the PA1698 placental IHC(P) caption does not state a fixative (selected caption PA1698). Record the actual fixative, fixation duration and processing history for each specimen, then compare adjacent sections processed with the same citrate pH 6.0, 95–98 °C, 20-minute retrieval (standard IHC practice; page retrieval rule). Include a known positive tissue and a no-primary control in each run to distinguish a specimen-level failure from broadly weak detection (HPA tissue IHC; standard IHC practice). Do not assign a fixation effect to CYP11A1 solely from its mitochondrial location, lack of annotated glycosylation or HPA staining pattern (UniProt P05108; HPA tissue IHC).
What staining pattern should count as correctly localised CYP11A1?
Expect granular cytoplasmic chromogen in appropriate cells, consistent with HPA tissue IHC and CYP11A1 localisation on the matrix side of the mitochondrial inner membrane (HPA tissue IHC; UniProt P05108). At routine light-microscope resolution, score the cellular granular pattern rather than claiming that individual membrane faces are resolved (standard IHC practice). Compare expected populations, including adrenal zona fasciculata cells, placental cytotrophoblasts and testicular Leydig cells, with adjacent morphology on a counterstained section (HPA tissue IHC; standard IHC practice). Predominantly nuclear or uniformly extracellular deposits warrant a repeat with a no-primary control and the specified 20-minute retrieval before assigning them to CYP11A1 (UniProt P05108; page retrieval rule; standard IHC practice).
Can this IHC stain distinguish CYP11A1 isoforms or a processed epitope?
The record lists 2 isoforms and a processed chain spanning residues 40–521, but supplies no antibody epitope or isoform-specific staining evidence (UniProt P05108). Therefore, report positive paraffin-section staining as CYP11A1 immunoreactivity, without assigning it to either isoform or a particular terminus (UniProt P05108; standard IHC practice). Check the catalog antibody’s documented immunogen and epitope, if available, before interpreting a negative result as loss of one isoform (standard IHC practice). Keep retrieval at citrate pH 6.0 for the initial comparison, and assess any alternative condition on adjacent sections with identical controls (page retrieval rule; standard IHC practice).
How could IF help check an ambiguous CYP11A1 IHC pattern?
Use IF as a separate validation experiment, since the supplied PA1698 evidence documents placental IHC(P) and does not establish an IF protocol (selected caption PA1698). Multiplex CYP11A1 with a validated marker for the expected cell population, such as a cytotrophoblast marker in placenta, and assess whether granular cytoplasmic signal occurs in marker-positive cells (HPA tissue IHC; standard IF practice). Choose fluorophores after examining unstained tissue in each channel so tissue autofluorescence does not masquerade as CYP11A1 signal (standard IF practice). For an epitope on the matrix side of the mitochondrial inner membrane, optimise permeabilisation empirically and use no-primary controls; epitope accessibility for this antibody is undocumented (UniProt P05108; standard IF practice).
How do I separate CYP11A1 signal from chromogenic background?
Inspect no-primary and detection-only controls alongside the stained section; signal persisting in those controls implicates the detection workflow rather than specific CYP11A1 binding (standard IHC practice). Quench endogenous peroxidase before an HRP/DAB workflow, and compare blocked and unblocked sections if diffuse or cell-associated brown deposits persist (standard IHC practice). Adjust antibody incubation and blocking only one variable at a time while retaining the citrate pH 6.0, 20-minute retrieval for the first comparison (page retrieval rule; standard IHC practice). Favor granular cytoplasmic staining in documented positive cells over diffuse staining in HPA-negative populations when deciding whether background has been reduced (HPA tissue IHC; standard IHC practice).
How should I quantify CYP11A1 across paraffin sections? ⚠ ANSWER MARKED FOR VERIFICATION
Define the cell population and analysis area before scoring; HPA identifies adrenal zona fasciculata cells, placental cytotrophoblasts and testicular Leydig cells as positive populations (HPA tissue IHC; standard IHC practice). Report the percentage of positive target cells and an H-score from intensity grades 0–3, or report positive-cell density per mm² when cell counts are reliable (standard IHC practice). Normalise counts to viable target cells or a defined viable tissue area, rather than total section area containing empty space or necrosis (standard IHC practice). Apply the same retrieval, detection, counterstain, thresholds and control-based background subtraction to every compared section (page retrieval rule; standard IHC practice).
When is CYP11A1 staining convincing rather than artefactual?
A convincing positive shows granular cytoplasmic staining in an expected cell population, such as placental cytotrophoblasts in the documented PA1698 IHC(P) tissue, while no-primary controls remain clear (selected caption PA1698; HPA tissue IHC; standard IHC practice). Nuclear-only staining conflicts with the recorded mitochondrial inner-membrane location and merits review before being called positive (UniProt P05108; standard IHC practice). Treat staining confined to section edges, necrotic areas or cells that also stain in a no-primary control as suspect, including possible endogenous enzyme activity in HRP/DAB detection (standard IHC practice). Confirm the pattern across intact areas and compare with an HPA-negative cell population under the same 20-minute retrieval and detection conditions (HPA tissue IHC; page retrieval rule; standard IHC practice).
Boster reagents
Best CYP11A1 / Cholesterol side-chain cleavage enzyme, mitochondrial IHC Antibodies
PA1698 has human placenta IHC images for paraffin and frozen sections (PA1698 image captions). The catalog provides no IF image (catalog: PA1698 IF image alts).
Real IHC data
Anti-CYP11A1 Antibody ®
Cat # PA1698
PA1698 is listed for human IHC and WB (catalog: PA1698 applications and reactivity). Its images show human placenta IHC in paraffin and frozen sections (PA1698 image captions).
Which to pick: For tissue IHC, choose PA1698 for human paraffin sections; its own placenta caption documents IHC(P), with a listed concentration of 0.5–1 μg/ml (PA1698 IHC(P) image caption; catalog: PA1698 IHC dilution). The paraffin caption does not report the fixative (PA1698 IHC(P) image caption). There is no catalog-supported IF/ICC or nonhuman choice here: PA1698 lists Human and IHC/WB, has no IF image or dilution, and reports no clone (catalog: PA1698 reactivity, applications, IF fields and clone).
Each figure is that product's own IHC / IF validation image from its datasheet.
References
- UniProt Consortium. UniProt entry P05108 (CP11A_HUMAN, Cholesterol side-chain cleavage enzyme, mitochondrial).
- Human Protein Atlas. CYP11A1 tissue IHC expression (reliability: Enhanced).
- Human Protein Atlas. CYP11A1 subcellular location (ICC-IF): Highest expression in HEL: 81.9 nTPM.
- Human Protein Atlas. CYP11A1 antibody validation summary (1 antibodies).
- Immunohistochemical expression of CYP11A1, CYP11B, CYP17, and HSD3B2 in functional and nonfunctional canine adrenocortical tumors. Journal of veterinary internal medicine 2024 — PMC11586580.
- Prenatal linuron exposure disrupts adrenal steroidogenesis and induces adrenal insufficiency in male rat offspring. Current research in toxicology 2025 — PMC12375238.
- Monocyte Chemoattractant Protein-1 stimulates the differentiation of rat stem and progenitor Leydig cells during regeneration. BMC developmental biology 2020 — PMC7541273.
- The Production of Testosterone and Gene Expression in Neonatal Testes of Rats Exposed to Diisoheptyl Phthalate During Pregnancy is Inhibited. Frontiers in pharmacology 2021 — PMC8072358.
- PubMed PMID:3024157 — UniProt-cited evidence.
- PubMed PMID:3038854 — UniProt-cited evidence.
- PubMed PMID:14702039 — UniProt-cited evidence.
Immunohistochemistry protocol sheet for CYP11A1 (Cholesterol side-chain cleavage enzyme, mitochondrial). Expected localisation Granular cytoplasm (HPA tissue IHC); mitochondrial inner membrane, matrix side (UniProt).. Antigen retrieval: Citrate pH 6.0 HIER, 95–98 °C, 20 min (rule: cytoplasmic / membrane antigen). Validated IHC antibody: PA1698 at 0.5-1μg/ml (the product's own IHC validation image is shown). Controls (HPA): positive Adrenal gland (Cells in zona fasciculata); negative Adipose tissue. 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 PA1698); 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-CYP11A1, 0.5-1μg/ml (datasheet PA1698); 9. Primary incubation: Overnight at 4 °C (standard). Watch for: Fixation: Keep paraffin-section fixation consistent across samples. (standard IHC practice; not target-specific); Caveat: Expression varies by tissue and cell type (HPA tissue IHC).; Isoform / epitope: Two isoforms; whether PA1698 detects both is unknown (UniProt; catalog).; Regulation: High in adrenal gland, placenta and testis (HPA tissue IHC).. Evidence: UniProt P05108, HPA tissue IHC · Enhanced, HPA cell-line RNA · Highest expression in HEL: 81.9 nTPM, Datasheet PA1698, PMC11586580, PMC12375238. QR code links to https://www.bosterbio.com/bosterbio-gene-info-cards/CYP11A1/immunohistochemistry-ihc-guide.