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S100A2 / Protein S100-A2 · IHC design guide
Design Immunohistochemistry for S100A2
Plan S100A2 chromogenic IHC in paraffin sections using the catalog antibody at 1:25 (datasheet M03698). Use bronchial respiratory or esophageal squamous epithelium as positive tissue and assess cytoplasmic and nuclear staining (HPA tissue IHC).
Evidence assembled Oct 2026 · For research use; verify linked source records and product datasheet before use
S100A2 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 and nuclear staining in urothelium and epithelium (HPA tissue IHC) | |
| Staining pattern | Urothelial, respiratory and squamous cells: cytoplasm and nuclei (HPA tissue IHC) | |
| Antigen retrieval | Citrate pH 6 HIER, heat-mediated (datasheet M03698) | |
| Positive control | Bronchus+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 (selected-SKU IHC image M03698); keep fixation consistent (standard IHC practice; not target-specific) | |
| Caveat | Cell-type restriction may obscure staining in mixed tissue (HPA tissue IHC) | |
| Regulation | No expression regulator annotated (UniProt) | |
| Isoform / epitope | No annotated isoforms; one 1–98 chain with no processing (UniProt) |
Section 1
Recommended S100A2 IHC & IF Protocols
The catalog antibody's citrate pH 6 IHC-P protocol (datasheet M03698) is followed by 3 published S100A2 IHC protocols (PMC3507318; PMC4324434; PMC4750537).
| Sample | Formaldehyde-fixed, paraffin-embedded human lung tissue (datasheet M03698) |
| Fixation | Image formalin-fixed; duration unreported (datasheet M03698); 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 M03698); 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 | Mouse monoclonal (clone 1592CT417.84.81) anti-S100A2, 1:25 (datasheet M03698) |
| Primary incubation | 1 hours at 37°C (datasheet M03698) |
| Detection | HRP-polymer secondary, DAB chromogen 5–10 min (standard) |
| Counterstain | Hematoxylin, blue, dehydrate and mount (standard) |
| Expected result | S100A2-positive staining in respiratory epithelial cells of bronchus (HPA tissue IHC: High). HPA tissue profile: Cytoplasmic and nuclear expression in urothelium, respiratory and squamous epithelium. No signal in the no-primary control. |
💡Decision noteStart with citrate pH 6 heat retrieval (datasheet M03698); compare the published high-pH and Tris-EDTA pH 8.0 conditions if staining needs optimization (PMC3507318; PMC4750537).
Section 2
What Is the Expected S100A2 Staining Pattern?
S100A2 should stain the cytoplasm and nuclei of selected epithelial cells, especially respiratory and squamous epithelium and urothelium (HPA tissue IHC: Enhanced; cytoplasmic and nuclear expression). Keratinocytes are among the epithelial cells reported to express it (UniProt P29034: tissue specificity). S100A2 has no transmembrane segment, so a membrane-only IHC pattern would need scrutiny (UniProt P29034: topology).
| Respiratory or squamous epithelial cells show cytoplasmic and nuclear staining, with nearby cell types less conspicuous. | This fits the reported distribution and compartments (HPA tissue IHC: cytoplasmic and nuclear expression in respiratory and squamous epithelium). Bronchial respiratory and esophageal squamous epithelial cells are useful positive references because each is reported at a High level (HPA tissue IHC: Bronchus and Esophagus, High). |
| Staining is confined to cell borders, with little or no cytoplasmic or nuclear signal. | A membrane-only pattern does not match the predominant tissue IHC pattern (HPA tissue IHC: cytoplasmic and nuclear expression). Plasma membrane is an additional ICC-IF location, so some peripheral signal is possible; assess the overall pattern before rejecting it (HPA subcellular: additional plasma membrane location, approved). |
| Strong signal appears in cells scored as negative, such as adipocytes or bone marrow hematopoietic cells. | Those cell types are reported as Not detected (HPA tissue IHC: adipose adipocytes and bone marrow hematopoietic cells). Check cell identity, cross-reactivity, and endogenous chromogenic activity with appropriate controls (general IHC practice). A negative score for breast adipocytes must not be applied to all breast epithelial cells (HPA tissue IHC: breast adipocytes, Not detected; UniProt P29034: normal mammary epithelial subset). |
| A uniform haze covers epithelium, stroma, and empty areas of the section. | That distribution does not provide interpretable cell-specific localization (general IHC practice). Check the no-primary control and detection reagents, then reassess blocking, washing, and antibody concentration under the assay's validated conditions (general IHC practice). |
| Known-positive bronchial respiratory or esophageal squamous epithelium has no detectable staining. | An absent signal in these High-level references leaves the run unresolved (HPA tissue IHC: Bronchus and Esophagus, High). Verify tissue identity, primary antibody performance, detection chemistry, and the assay's documented retrieval settings before interpreting other samples as negative (general IHC practice). |
💡Expected S100A2 appearanceA convincing positive result shows conspicuous cytoplasmic and nuclear staining in the expected epithelial cells, particularly High-level bronchial respiratory or esophageal squamous epithelium; uniform haze or strong staining of HPA-negative cell types is suspect (HPA tissue IHC: profile, positive and negative cell scores; general IHC practice).
| Tissue and cell selection | Use cell-level reference patterns: bronchial respiratory cells, esophageal squamous cells, nasopharyngeal respiratory cells, and skin hair follicles are High; cervical and oral squamous cells are Medium (HPA tissue IHC: positive cell scores). Salivary glandular cells are Low, making them a weaker positive reference (HPA tissue IHC: Salivary gland, Low). |
| Compartments and protein topology | Expect cytoplasmic and nuclear tissue staining (HPA tissue IHC: profile). ICC-IF places S100A2 mainly in nucleoplasm and cytosol, with additional nucleolar and plasma membrane localization (HPA subcellular: approved locations). The protein has no transmembrane segment (UniProt P29034: topology). |
| Antibody evidence | The tissue profile has Enhanced reliability because antibody staining is consistent with RNA expression data (HPA tissue IHC: reliability). Three listed antibodies have Enhanced IHC status: HPA062451, CAB002600, and CAB047340 (HPA antibodies: IHC validation). This supports using the reported pattern as a reference, while local controls still determine whether an individual run is interpretable (general IHC practice). |
| Processing and isoform annotation | The record describes one chain spanning residues 1–98, with no signal peptide, propeptide, annotated glycosylation sites, or listed isoforms (UniProt P29034: processing, glycosylation, isoforms). These annotations do not establish how fixation or retrieval affects IHC signal; target-specific fixation sensitivity is unreported in the supplied sources. |
| IF/ICC Q&A: where should signal appear? | Mainly in nucleoplasm and cytosol, with possible nucleolar and plasma membrane signal (HPA subcellular: approved locations). This ICC-IF observation informs compartment interpretation; tissue cell-type expectations come from HPA tissue IHC (HPA tissue IHC: profile). |
| Situation | Likely cause | Next action |
|---|---|---|
| No signal in a positive reference section | The result conflicts with High staining reported for bronchial respiratory and esophageal squamous cells (HPA tissue IHC: positive cell scores); the failed step is not identified by that comparison alone. | Confirm the intended cells are present, then check the primary antibody, detection reagents, counterstain, and documented retrieval conditions with run controls (general IHC practice). |
| Signal appears only at cell borders | Predominantly border-only staining differs from the reported cytoplasmic and nuclear tissue pattern (HPA tissue IHC: profile), although membrane localization is an additional ICC-IF finding (HPA subcellular: plasma membrane, approved). | Inspect nuclear and cytoplasmic compartments in the positive reference and compare with a no-primary control before assigning a specific artefact (general IHC practice). |
| Strong staining in adipocytes or bone marrow hematopoietic cells | Those cell types are scored Not detected (HPA tissue IHC: negative cell scores); cross-reactivity or endogenous chromogenic activity are possibilities, not established causes (general IHC practice). | Verify the cell type, examine a no-primary control, and review blocking and detection controls before scoring the signal as S100A2 (general IHC practice). |
| Diffuse staining obscures cell boundaries | Broad background prevents assessment of the expected epithelial compartments (HPA tissue IHC: profile; general IHC practice). | Compare a no-primary control, check washing and blocking, and use the documented antibody dilution as the starting point for assay optimization (general IHC practice). |
| A negative result is inferred from breast adipocytes | The HPA negative score is specifically for breast adipocytes (HPA tissue IHC: breast adipocytes, Not detected); UniProt reports expression in a subset of normal mammary epithelial cells (UniProt P29034: tissue specificity). | Score identified cell populations separately and include a positive epithelial reference when assessing run performance (general IHC practice). |
| A weak sample is treated as proof that the run failed | S100A2 staining varies by tissue and cell type: salivary glandular cells are Low, while bronchial respiratory and esophageal squamous cells are High (HPA tissue IHC: cell scores). | Judge run performance against a High-level reference and its controls, then report the sample's intensity and cell distribution separately (HPA tissue IHC: positive cell scores; general IHC practice). |
Experiment evidence
IHC & IF images showing S100A2 staining
M03698 · IHCM03698 staining S100A2 in human lung tissue sections by Immunohistochemistry (IHC-P -paraformaldehyde-fixed, paraffin-embedded sections). Ti
M03698 · IHCM03698 staining S100A2 in human skin tissue sections by Immunohistochemistry (IHC-P -paraformaldehyde-fixed, paraffin-embedded sections). Ti
M03698 · IFImmunofluorescent analysis of 4% paraformaldehyde-fixed, 0.1% Triton X-100 permeabilized HeLa (human cervical epithelial adenocarcinoma cell
HPA · Cerebral cortexHuman Protein Atlas IHC, Cerebral cortex. Source: https://www.proteinatlas.org/ENSG00000196754-S100A2/tissue/cerebral+cortex#imid_17822563
HPA · EsophagusHuman Protein Atlas IHC, Esophagus. Source: https://www.proteinatlas.org/ENSG00000196754-S100A2/tissue/esophagus#imid_17822535
HPA · ColonHuman Protein Atlas IHC, Colon. Source: https://www.proteinatlas.org/ENSG00000196754-S100A2/tissue/colon#imid_17822497
HPA · LiverHuman Protein Atlas IHC, Liver. Source: https://www.proteinatlas.org/ENSG00000196754-S100A2/tissue/liver#imid_17822482
HPA · ICC-IF A-431Human Protein Atlas immunofluorescence, A-431, antibody CAB002600; green = S100A2, blue = nucleus, red = microtubules.
HPA · ICC-IF A-431Human Protein Atlas immunofluorescence, A-431, antibody CAB002600; green = S100A2, blue = nucleus, red = microtubules.
← swipe / scroll for more images →
Real IHC / IF data behind the staining-pattern expectations in this section.
Sample controls for S100A2 IHC & IF
🧪Run esophagus first: squamous epithelial cells should stain strongly (HPA: High in esophageal squamous epithelial cells). Use adipose tissue as a negative, where adipocytes should remain unstained (HPA: Not detected in adipocytes); on the esophagus slide, assess non-epithelial areas for background rather than assuming every such cell is S100A2-negative (HPA: staining annotation is for squamous epithelial cells).
Positive control tissue: Bronchus (Respiratory epithelial cells, HPA High)
Negative control tissue: Adipose tissue (HPA Not detected)
ICC-IF cell lines (HPA subcellular resource): HPA ICC-IF images show S100A2 in A-431, U-251MG, U2OS, with annotated localisation: Nucleoplasm (approved), Cytosol (approved) (HPA subcellular).
Technical controls: Include a no-primary, secondary-only control and an isotype control matched to the primary antibody’s host species and immunoglobulin class; use an S100A2 knockout sample or peptide competition, if the immunizing peptide is available, to test specificity (standard IHC practice). Quench endogenous peroxidase for chromogenic HRP detection and check endogenous biotin if using the caption’s biotinylated secondary antibody (standard IHC practice; M03698 tissue-IHC caption: biotinylated secondary).
⚠️Feasibility: A target-specific fixation window or fixation effect is unreported, and the selected M03698 caption’s fixative field is unreported (M03698 tissue-IHC caption). The caption uses heat-mediated citrate retrieval at pH 6, but it does not establish that S100A2 staining depends on that retrieval method (M03698 tissue-IHC caption). The supplied evidence does not establish whether frozen sections or IF are easier; on esophageal sections, check for nonspecific keratin-associated background when interpreting epithelial staining (standard IHC/IF practice).
HPA tissue IHC evidence for S100A2
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 |
|---|---|---|---|---|
| Bronchus | Respiratory epithelial cells | High | Protein (IHC) | HPA → |
| Esophagus | Squamous epithelial cells | High | Protein (IHC) | HPA → |
| Nasopharynx | Respiratory epithelial cells | High | Protein (IHC) | HPA → |
| Skin | Hair follicles | High | Protein (IHC) | HPA → |
| Cervix | Squamous epithelial 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 | Glandular 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 S100A2 IHC Tips
Troubleshoot S100A2 staining in paraffin sections by checking retrieval, cell type, compartment and controls before comparing chromogenic signal across samples.
Which retrieval should I try first for weak S100A2 staining?
Start with heat-mediated citrate retrieval at pH 6 for paraffin sections (datasheet M03698). The selected tissue image used this retrieval with a 1:25 primary antibody incubation for 1 hour at 37°C, so use that image as a starting comparison rather than proof that the conditions suit every specimen (caption M03698). If staining is weak, check that sections were fully deparaffinised and that the retrieval bath reached a consistent temperature before changing chemistry (standard IHC practice). Then compare a second retrieval condition on adjacent sections while keeping antibody dilution and detection constant (standard IHC practice). Score epithelial signal against background on the same slide (HPA tissue IHC; standard IHC practice).
Could fixation explain weak or uneven S100A2 IHC staining?
Target-specific sensitivity to fixation is unknown from the supplied evidence, so do not assign weak staining to a particular fixative without a controlled comparison. The selected image describes formaldehyde fixation of paraffin-embedded human lung sections, but it does not establish a fixation response curve for S100A2 (caption M03698). Compare sections with documented fixation histories under the same citrate pH 6 retrieval and antibody conditions (datasheet M03698; standard IHC practice). Check tissue preservation and staining at section edges before judging intensity (standard IHC practice). Use respiratory epithelial cells as an internal reference when present, while assessing morphology and signal together (HPA tissue IHC; standard IHC practice).
Should S100A2 staining be nuclear, cytoplasmic or membranous?
Expect nuclear and cytoplasmic staining in relevant epithelium on tissue sections (HPA tissue IHC). Cell imaging places S100A2 mainly in the nucleoplasm and cytosol, with additional nucleolar and plasma membrane localisation (HPA subcellular). Score nuclear and cytoplasmic compartments separately if their relative intensity changes between specimens (standard IHC practice). A membrane-only rim without convincing epithelial nuclear or cytoplasmic signal deserves review alongside morphology and detection controls (HPA tissue IHC; standard IHC practice). S100A2 has no annotated transmembrane segment, so membrane staining alone should not be treated as evidence of an integral membrane protein (UniProt P29034 topology).
How can epitope choice affect interpretation of S100A2 staining?
The supplied record lists one 98-residue S100A2 chain and no isoforms, signal peptide, propeptide, glycosylation sites or modified residues (UniProt P29034). Its two EF-hand regions span residues 13–48 and 51–86; the antibody epitope is not supplied, so avoid attributing a staining change to either region (UniProt P29034; supplied antibody evidence). If signal differs across specimens, compare matched sections with consistent retrieval and detection before proposing epitope masking (standard IHC practice). Keep antibody identity and dilution recorded for every run; the selected image used SKU M03698 at 1:25 (caption M03698). An independent antibody with a disclosed epitope can help investigate discordance, provided its IHC performance is established (standard IHC practice).
How should I check S100A2 localisation by IF alongside this IHC guide?
For the separate IF/ICC workflow, multiplex S100A2 with a marker of the expected epithelial cell type and inspect each channel independently (HPA tissue IHC; standard IF practice). Choose fluorophores after measuring specimen autofluorescence, and place the weaker signal in a channel with lower background where feasible (standard IF practice). Permeabilise when assessing the expected nucleoplasmic or cytosolic signal, and titrate that step to preserve morphology (HPA subcellular; standard IF practice). Include single-stain and secondary-only controls to assess bleed-through and background (standard IF practice). Do not transfer the selected paraffin-section retrieval or 1:25 dilution directly to IF/ICC without validation (caption M03698; standard IF practice).
What should I check when S100A2 DAB staining appears diffuse?
First inspect a no-primary control to separate detection-system background from primary-antibody staining (standard IHC practice). For chromogenic detection, verify the endogenous peroxidase block and compare DAB development across matched sections (standard IHC practice). The selected image used 3% BSA blocking for 0.5 hour at room temperature and an undiluted biotinylated secondary antibody; these are image conditions, not a demonstrated solution for every specimen (caption M03698). Check whether diffuse signal follows folds, damaged areas or tissue edges rather than intact epithelial cells (standard IHC practice). Evaluate respiratory or squamous epithelium against nearby unstained structures in context (HPA tissue IHC; standard IHC practice).
How should I quantify S100A2 across paraffin sections? ⚠ ANSWER MARKED FOR VERIFICATION
Define the epithelial compartment and scoring region before measuring chromogenic signal (HPA tissue IHC; standard IHC practice). Report the percentage of positive epithelial cells and, if intensity matters, an H-score using 0–3 intensity categories for a 0–300 range (standard IHC practice). Score nuclear and cytoplasmic staining separately because both occur in tissue (HPA tissue IHC). Normalise cell counts or positive area to the number of eligible epithelial cells or epithelial area, rather than total section area (standard IHC practice). Keep retrieval, antibody dilution, DAB development and image thresholds consistent, and document excluded folds or necrosis (standard IHC practice).
How do I distinguish genuine S100A2 signal from artefact?
Give greatest weight to staining in intact respiratory or squamous epithelial cells, where tissue evidence supports S100A2 expression (HPA tissue IHC). Nuclear and cytoplasmic signal fits the tissue profile; isolated staining in an unexpected cell type or compartment needs corroboration (HPA tissue IHC; standard IHC practice). Compare suspicious signal with adjacent tissue morphology and a no-primary control, particularly at section edges and necrotic areas (standard IHC practice). If DAB persists without primary antibody, reassess endogenous peroxidase blocking and detection conditions (standard IHC practice). A negative result in one field does not establish absence throughout a heterogeneous specimen; sample comparable epithelial regions before drawing that conclusion (standard IHC practice).
Boster reagents
Best S100A2 / Protein S100-A2 IHC Antibodies
M03698 has IHC images from human lung and skin paraffin sections and an IF image from HeLa cells (M03698 image captions). Human is the only listed reactive species (M03698 catalog).
Real IHC data
Anti-S100A2 Antibody
Cat # M03698
M03698 is listed for IHC-P and shown staining human lung and skin paraffin sections (M03698 catalog and IHC captions). M03698 is also listed for IF and shown staining paraformaldehyde-fixed, permeabilized HeLa cells (M03698 catalog and IF caption).
Which to pick: Choose M03698 for human tissue IHC: it is a mouse monoclonal antibody listed for IHC-P, and its own captions show staining in paraffin-embedded lung and skin sections with formaldehyde fixation reported (M03698 catalog and IHC captions). For IF/ICC, the same SKU is listed for IF and has an image from HeLa cells (M03698 catalog and IF caption). Its listed reactivity is Human, so the payload provides no basis to recommend it for another species (M03698 catalog).
Each figure is that product's own IHC / IF validation image from its datasheet.
References
- UniProt Consortium. UniProt entry P29034 (S10A2_HUMAN, Protein S100-A2).
- Human Protein Atlas. S100A2 tissue IHC expression (reliability: Enhanced).
- Human Protein Atlas. S100A2 subcellular location (ICC-IF): Mainly localized to the nucleoplasm and cytosol. In addition localized to the nucleoli and plasma membrane..
- Human Protein Atlas. S100A2 antibody validation summary (3 antibodies).
- S100A2 Is a Prognostic Biomarker Involved in Immune Infiltration and Predict Immunotherapy Response in Pancreatic Cancer. Frontiers in immunology 2021 — PMC8650155.
- Prognostic significance of different immunohistochemical S100A2 protein expression patterns in patients with operable nonsmall cell lung carcinoma. OncoTargets and therapy 2012 — PMC3507318.
- Prognostic significance of cytoplasmic S100A2 overexpression in oral cancer patients. Journal of translational medicine 2015 — PMC4324434.
- Overexpression of the S100A2 protein as a prognostic marker for patients with stage II and III colorectal cancer. International journal of oncology 2016 — PMC4750537.
- PubMed PMID:1372446 — UniProt-cited evidence.
- PubMed PMID:9481475 — UniProt-cited evidence.
- PubMed PMID:16710414 — UniProt-cited evidence.
Immunohistochemistry protocol sheet for S100A2 (Protein S100-A2). Expected localisation Cytoplasmic and nuclear staining in urothelium and epithelium (HPA tissue IHC). Antigen retrieval: Citrate pH 6 HIER, heat-mediated (datasheet M03698). Validated IHC antibody: M03698 at 1:25 (the product's own IHC validation image is shown). Controls (HPA): positive Bronchus (Respiratory epithelial cells); negative Adipose tissue. IHC-P workflow on paraffin sections. Protocol steps: 1. Sample: Formaldehyde-fixed, paraffin-embedded human lung tissue (datasheet M03698); 2. Fixation: Image formalin-fixed; duration unreported (datasheet M03698); 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 (datasheet M03698); 20 min, 95–100 °C (standard); 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: Mouse monoclonal (clone 1592CT417.84.81) anti-S100A2, 1:25 (datasheet M03698); 9. Primary incubation: 1 hours at 37°C (datasheet M03698). Watch for: Fixation: Formaldehyde-fixed paraffin sections (selected-SKU IHC image M03698); keep fixation consistent (standard IHC practice; not target-specific); Caveat: Cell-type restriction may obscure staining in mixed tissue (HPA tissue IHC); Isoform / epitope: No annotated isoforms; one 1–98 chain with no processing (UniProt); Regulation: No expression regulator annotated (UniProt). Evidence: UniProt P29034, HPA tissue IHC · Enhanced, HPA ICC-IF · Mainly localized to the nucleoplasm and cytosol. In addition…, Datasheet M03698, PMC3507318, PMC4324434. QR code links to https://www.bosterbio.com/bosterbio-gene-info-cards/S100A2/immunohistochemistry-ihc-guide.