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CSK / Tyrosine-protein kinase CSK · IHC design guide
Design Immunohistochemistry for CSK
Plan CSK staining in paraffin sections using the catalog antibody at 0.5–1 μg/mL (datasheet: PB9102). Compare cytoplasmic staining across tissues, including immune-cell subsets (HPA tissue IHC).
Evidence assembled Oct 2026 · For research use; verify linked source records and product datasheet before use
CSK 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; a membrane pool is possible (HPA tissue IHC: cytoplasm; UniProt: membrane) | |
| Staining pattern | Cytoplasmic in several tissues, including immune-cell subsets (HPA tissue IHC) | |
| Antigen retrieval | Citrate pH 6 HIER, heat-mediated (datasheet PB9102) | |
| Positive control | Testis+4 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 conditions consistent across sections. (standard IHC practice; not target-specific) | |
| Caveat | Antibody staining has low consistency with RNA expression (HPA tissue IHC) | |
| Regulation | Tissue-dependent expression (HPA tissue IHC) | |
| Isoform / epitope | No listed isoforms or extracellular domain (UniProt) |
Section 1
Recommended CSK IHC & IF Protocols
The catalog antibody’s IHC-P protocol is accompanied by published CSK staining protocols for breast cancer tissue microarrays (PMC6077722) and mouse and human pancreatic tumors (PMC3104672).
| Sample | Paraffin-embedded human tonsil tissues; fixative not specified (datasheet PB9102) |
| Fixation | Image fixative and duration unreported (datasheet PB9102); 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 PB9102) |
| Peroxidase block | 3% H2O2, 10 min, room temperature (standard) |
| Blocking | 10% goat serum (datasheet PB9102) |
| Primary antibody | Rabbit anti-CSK, 0.5-1μg/ml (datasheet PB9102) |
| Primary incubation | Overnight at 4 °C (datasheet PB9102) |
| Detection | Streptavidin-biotin complex (SABC), DAB chromogen (datasheet PB9102) |
| Counterstain | Hematoxylin, blue, dehydrate and mount (standard) |
| Expected result | CSK-positive staining in spermatogonia cells of testis (HPA tissue IHC: High). HPA tissue profile: Cytoplasmic expression in several tissues, including subsets of immune cells. No signal in the no-primary control. |
💡Decision noteStart with heat-mediated citrate pH 6 retrieval for the catalog antibody (datasheet PB9102). For the published breast tumor protocol, use EDTA pH 9 (PMC6077722).
Section 2
What Is the Expected CSK Staining Pattern?
CSK should stain mainly in the cytoplasm, with possible membrane-associated signal because it can be recruited to the plasma membrane (UniProt P41240 localization and function). In paraffin sections, expect staining in selected cells, including spermatogonia and subsets of immune cells (HPA tissue IHC). Interpret intensity cautiously: HPA rates tissue IHC reliability “Approved” but reports low consistency between staining and RNA expression (HPA tissue IHC). CSK has no transmembrane segment (UniProt P41240 topology).
| Cytoplasmic staining is High in testicular spermatogonia; lymph-node non-germinal-center cells stain Medium (HPA tissue IHC). | This supports the expected cell-selective pattern. Compare the labeled cells and their compartment, rather than scoring a whole section as positive; HPA reports cytoplasmic expression across several tissues, including subsets of immune cells (HPA tissue IHC). |
| Staining is predominantly nuclear, with little cytoplasmic signal. | A nuclear-dominant pattern conflicts with the mainly cytoplasmic localization reported for CSK (UniProt P41240 localization). Review morphology and the counterstain, then compare a known-positive cell population before assigning the nuclear signal to CSK (HPA tissue IHC; standard IHC practice). |
| Strong staining appears in adipocytes or cardiomyocytes, where CSK was not detected by HPA (HPA tissue IHC). | These cell types warrant scrutiny for cross-reactivity or detection-system activity; an HPA “not detected” result is an observed staining level, not proof that every specimen must be negative (HPA tissue IHC; standard IHC practice). Check cell identity and a no-primary control (standard IHC practice). |
| Color spreads across tissue structures without a clear cellular boundary. | Diffuse signal is difficult to interpret as the reported cytoplasmic, cell-selective pattern (HPA tissue IHC). Compare a no-primary control and review blocking, washing and chromogen development; background from detection reagents can obscure cellular staining (standard IHC practice). |
| Spermatogonia show no detectable staining in a section expected to be positive (HPA: High in spermatogonia). | The absent signal leaves the assay unresolved; it does not establish CSK absence in that specimen (HPA tissue IHC; standard IHC practice). Verify that the cells are present, then review the catalog antibody’s IHC-P instructions and detection controls (standard IHC practice). |
💡Expected CSK appearanceA convincing positive result is chiefly cytoplasmic staining in identified cells, reaching High intensity in spermatogonia or Medium in lymph-node non-germinal-center cells; nuclear-dominant or indiscriminate staining calls for review (HPA tissue IHC; UniProt P41240 localization).
| Cell compartment and membrane recruitment | CSK is mainly cytoplasmic and can be recruited to the plasma membrane through binding partners; it has no transmembrane segment (UniProt P41240 localization, function and topology). Interpret limited membrane-associated signal in its cellular context rather than requiring a continuous membrane outline. |
| Choice of positive and comparison cells | HPA reports High staining in spermatogonia and Medium staining in lymph-node non-germinal-center cells (HPA tissue IHC). It reports no detection in adipocytes and cardiomyocytes (HPA tissue IHC). Compare those named cells; tissue-wide labels can hide differences between cell populations. |
| Strength of tissue evidence | HPA labels CSK tissue IHC “Approved” while noting low consistency between antibody staining and RNA expression (HPA tissue IHC). Three listed antibodies have IHC “Approved” status, but the supplied record does not mark them IHC “Enhanced” (HPA antibodies). Treat an unexpected pattern as a result to verify. |
| Processing and epitope limits | UniProt lists no signal peptide or propeptide and a CSK chain spanning residues 2–450 (UniProt P41240 processing). The supplied sources give no antibody epitope or target-specific fixation-sensitivity data; they therefore cannot justify a CSK-specific antigen-retrieval prediction (UniProt P41240; HPA tissue IHC). |
| Situation | Likely cause | Next action |
|---|---|---|
| No signal in identifiable spermatogonia despite their reported High staining (HPA tissue IHC). | Target-specific fixation effects are not established by the supplied assay evidence. Verify with a matched IHC source before attributing a result to fixation. | Confirm cell identity, follow the catalog antibody’s IHC-P instructions, and check that detection reagents work on an appropriate positive section (standard IHC practice). |
| Predominantly nuclear staining replaces the expected cytoplasmic pattern (UniProt P41240 localization). | Compartment assignment may be confounded by counterstain or nonspecific signal; nuclear-dominant localization is unsupported by the supplied CSK sources (standard IHC practice; UniProt P41240). | Inspect cells at higher magnification and compare a known-positive section and no-primary control before scoring nuclei as positive (standard IHC practice; HPA tissue IHC). |
| Adipocytes or cardiomyocytes stain strongly, although HPA reports not detected in those cell types (HPA tissue IHC). | Possible cross-reactivity or detection-system background requires evaluation; HPA staining levels alone do not identify the cause (HPA tissue IHC; standard IHC practice). | Confirm the stained cell type and compare no-primary controls. If enzyme-based detection is used, check the corresponding endogenous-activity block (standard IHC practice). |
| Diffuse chromogen obscures the cellular pattern. | Excess background can arise from blocking, washing or chromogen development in a general IHC workflow (standard IHC practice). | Compare a no-primary control, review the catalog IHC-P dilution instructions, and optimize blocking, washing and development time as needed (standard IHC practice). |
| A Medium HPA cell population appears weaker than spermatogonia (HPA tissue IHC). | Different intensities can reflect the reported cell-specific HPA pattern; HPA rates spermatogonia High and several other populations Medium (HPA tissue IHC). | Score the named cell populations separately and compare compartments before calling the weaker population negative (HPA tissue IHC; standard IHC practice). |
| Can IF/ICC show a different-looking CSK pattern? | HPA ICC-IF reports enhanced localization to vesicles and cytosol, while UniProt describes CSK as mainly cytoplasmic with some lipid-raft localization (HPA subcellular ICC-IF; UniProt P41240 localization). | Use the ICC-IF localization as context for fluorescence images; assess paraffin-section chromogenic staining against the tissue IHC cell and compartment observations (HPA subcellular ICC-IF; HPA tissue IHC). |
Experiment evidence
IHC & IF images showing CSK staining
PB9102 · IHCIHC analysis of CSK using anti-CSK antibody (PB9102). CSK was detected in paraffin-embedded section of human tonsil tissues. Heat mediated a
PB9102 · IHCIHC analysis of Csk using anti-Csk antibody (PB9102). Csk was detected in paraffin-embedded section of human tonsil tissues. Heat mediated a
HPA · Cerebral cortexHuman Protein Atlas IHC, Cerebral cortex. Source: https://www.proteinatlas.org/ENSG00000103653-CSK/tissue/cerebral+cortex#imid_3065552
HPA · ColonHuman Protein Atlas IHC, Colon. Source: https://www.proteinatlas.org/ENSG00000103653-CSK/tissue/colon#imid_6477702
HPA · LiverHuman Protein Atlas IHC, Liver. Source: https://www.proteinatlas.org/ENSG00000103653-CSK/tissue/liver#imid_6477703
HPA · KidneyHuman Protein Atlas IHC, Kidney. Source: https://www.proteinatlas.org/ENSG00000103653-CSK/tissue/kidney#imid_6477696
HPA · ICC-IF A-431Human Protein Atlas immunofluorescence, A-431, antibody HPA028425; green = CSK, blue = nucleus, red = microtubules.
HPA · ICC-IF A-431Human Protein Atlas immunofluorescence, A-431, antibody HPA028425; green = CSK, blue = nucleus, red = microtubules.
← swipe / scroll for more images →
Real IHC / IF data behind the staining-pattern expectations in this section.
Sample controls for CSK IHC & IF
🧪Run testis first and look for staining in spermatogonia (HPA: High in testis spermatogonia). Use adipose tissue as the negative tissue and assess its adipocytes (HPA: Not detected in adipocytes); on the testis slide, treat unstained neighboring cells as a background reference, without assuming they are confirmed CSK-negative.
Positive control tissue: Testis (Spermatogonia cells, HPA High)
Negative control tissue: Adipose tissue (HPA Not detected)
ICC-IF cell lines (HPA subcellular resource): HPA ICC-IF images show CSK in A-431, U-251MG, U2OS, HEK293, with annotated localisation: Vesicles (enhanced), Cytosol (enhanced) (HPA subcellular).
Technical controls: Include no-primary (secondary-only) and concentration-matched nonimmune rabbit IgG controls (selected PB9102 caption: rabbit primary), plus a CSK knockout sample as a biological negative if available. Check endogenous peroxidase and biotin background in testis because the caption uses biotin-based detection with DAB (selected PB9102 caption: biotinylated secondary, SABC, DAB).
⚠️Feasibility: A target-specific fixation window or fixation effect is unreported, and the selected PB9102 paraffin-section caption does not state a fixative. The caption uses heat retrieval in citrate buffer at pH 6 for 20 minutes, but does not establish that retrieval is required (selected PB9102 caption). Relative ease of frozen-section staining or IF and any testis-specific artefact are unreported in the supplied evidence.
HPA tissue IHC evidence for CSK
Comprehensive Human Protein Atlas IHC scoring per tissue (reliability: Approved — Low 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 |
|---|---|---|---|---|
| Testis | Spermatogonia cells | High | Protein (IHC) | HPA → |
| Caudate | Neuronal cells | Medium | Protein (IHC) | HPA → |
| Cerebellum | Cells in molecular layer | Medium | Protein (IHC) | HPA → |
| Cerebral cortex | Endothelial cells | Medium | Protein (IHC) | HPA → |
| Duodenum | Glandular 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 → |
| Cervix | Glandular cells | Not detected | Protein (IHC) | HPA → |
| Esophagus | Squamous epithelial cells | Not detected | Protein (IHC) | HPA → |
Section 3
Advanced CSK IHC Tips
Use the catalog antibody’s paraffin-section IHC example as a starting point, then judge CSK staining by cell type, compartment, and controls.
Which retrieval conditions should I use when CSK staining is weak?
Start with heat-mediated retrieval in citrate buffer at pH 6 for 20 minutes (datasheet PB9102). That is the retrieval used for the catalog antibody’s paraffin-embedded human tonsil example, whose fixative was not reported (datasheet PB9102). If staining remains weak, vary heating time in small steps while processing a known-positive section alongside the test section, and watch for tissue damage (standard IHC practice). Compare matched sections with and without retrieval before changing antibody concentration, because retrieval can alter both epitope exposure and background (standard IHC practice). Record the heating method and cooling conditions so comparisons remain interpretable (standard IHC practice).
Could fixation explain inconsistent CSK staining across paraffin sections?
The catalog example identifies paraffin-embedded tonsil but does not state its fixative, so CSK-specific fixation sensitivity is unknown (datasheet PB9102). Do not infer a preferred fixative from the reported tissue staining pattern or CSK’s intracellular location (HPA: tissue IHC; UniProt P41240: cytoplasm and cell membrane). Compare sections with documented fixation histories under the same citrate pH 6 retrieval and detection conditions (datasheet PB9102; standard IHC practice). Include a similarly processed positive control in each run, and examine morphology as well as staining intensity (standard IHC practice). Treat a fixation-related explanation as provisional until matched processing conditions support it (standard IHC practice).
Should CSK appear at the membrane or in the cytoplasm?
Expect mainly cytoplasmic staining, with possible membrane-associated signal because CSK also occurs in lipid rafts (UniProt P41240: subcellular location). CSK has no transmembrane segment; its recruitment near the plasma membrane involves interactions with phosphorylated membrane proteins or adapters (UniProt P41240: topology and function). HPA reports cytoplasmic staining in several tissues, including subsets of immune cells, while its cell-imaging summary lists cytosol and vesicles (HPA: tissue IHC; HPA: subcellular). Assess membrane accentuation against adjacent cytoplasm within the same cell and confirm cellular boundaries with the counterstain (standard IHC practice). Isolated nuclear staining needs further validation before being assigned to CSK (UniProt P41240: subcellular location).
How should epitope uncertainty affect my CSK IHC controls?
The supplied CSK record lists 0 isoforms and an SH3 domain at residues 9–70, SH2 at 82–171, and kinase domain at 195–449 (UniProt P41240: isoforms and domains). It does not identify the catalog antibody’s epitope, so do not attribute staining differences to recognition of a particular domain (supplied PB9102 caption; UniProt P41240). CSK also has documented modified residues, including phosphotyrosines and phosphoserine, but their effect on this antibody’s staining is unknown (UniProt P41240: modified residues). Evaluate specificity using an appropriate loss-of-target control where available and a matched positive section (standard IHC practice). Keep retrieval and detection conditions identical when comparing them (standard IHC practice).
How can I assess CSK by IF alongside an immune-cell marker?
For a separate IF assay, pair CSK with a marker such as CD68 to identify macrophages, a reported CSK-expressing cell type (UniProt P41240: tissue specificity; standard IF practice). Choose spectrally separated fluorophores and favor a far-red channel for a weaker signal when tissue autofluorescence interferes with shorter wavelengths (standard IF practice). After fixation, use a mild permeabilisation condition to reach cytosolic CSK; membrane-associated CSK is recruited to the cytoplasmic side through partner interactions (UniProt P41240: topology and function; standard IF practice). The PB9102 paraffin-section caption establishes a chromogenic IHC example, not IF performance (datasheet PB9102). Include single-label and secondary-only controls to assess bleed-through and nonspecific fluorescence (standard IF practice).
What should I check when DAB background obscures CSK?
Check the no-primary control first, then inspect whether diffuse DAB follows tissue edges, folds, or areas of poor preservation (standard IHC practice). The catalog example used 10% goat serum blocking, 1 μg/ml primary antibody overnight at 4°C, and a biotin-based DAB detection system (datasheet PB9102). For that detection approach, assess endogenous peroxidase activity and endogenous biotin as possible background sources, using suitable controls (standard IHC practice). If controls are clean but background persists, optimize primary concentration, wash stringency, and chromogen development on matched sections (standard IHC practice). Judge any reduction against preservation of the expected cytoplasmic signal (UniProt P41240: subcellular location).
How should I score CSK staining across mixed cell populations? ⚠ ANSWER MARKED FOR VERIFICATION
Define the cell population and compartment before scoring, because CSK staining is reported in subsets of immune cells and is mainly cytoplasmic (HPA: tissue IHC; UniProt P41240: subcellular location). Within each defined population, record percent-positive cells and intensity for an H-score, or count positive cells per mm² of viable tissue (standard IHC practice). Normalize cell counts to the measured viable tissue area, and report intensity within the selected cell population rather than across all cells (standard IHC practice). Keep thresholds, retrieval, imaging, and DAB development consistent across sections (standard IHC practice). Report cell composition and excluded damaged areas so changes in population abundance are not mistaken for changes in CSK staining (standard IHC practice).
How do I distinguish credible CSK positivity from staining artefact?
Credible staining should fit CSK’s mainly cytoplasmic location, allowing some membrane-associated signal, and should be evaluated in identified cells (UniProt P41240: subcellular location; standard IHC practice). HPA reports cytoplasmic expression in several tissues, including immune-cell subsets, but describes low consistency between antibody staining and RNA expression data (HPA: tissue IHC). Question dominant nuclear signal, staining limited to section edges or necrotic regions, and deposits also present in a no-primary control (UniProt P41240: subcellular location; standard IHC practice). Check endogenous peroxidase and biotin contributions when using the catalog example’s biotin-based DAB workflow (datasheet PB9102; standard IHC practice). Confirm disputed patterns with appropriate specificity controls before assigning biological meaning (standard IHC practice).
Boster reagents
Best CSK / Tyrosine-protein kinase CSK IHC Antibodies
Two anti-CSK antibodies list IHC and Human, Mouse, Rat reactivity (catalog: PB9102, M00799-2); PB9102 has a human tonsil paraffin-section IHC image (PB9102 IHC caption).
Real IHC data
Anti-Csk Antibody ®
Cat # PB9102
PB9102 lists IHC and Human, Mouse, Rat reactivity; its image shows chromogenic IHC in a paraffin-embedded human tonsil section (catalog: PB9102; PB9102 IHC caption). M00799-2 lists IHC and Human, Mouse, Rat reactivity, but has no supplied IHC image (catalog: M00799-2).
Which to pick: For tissue IHC, pick PB9102 because its own image documents staining in a paraffin-embedded human tonsil section; the fixative is unreported (PB9102 IHC caption). M00799-2 is a rabbit monoclonal IHC-listed option without a supplied IHC image; neither SKU lists IF/ICC, so neither has documented IF/ICC validation here (catalog: M00799-2, PB9102). For cross-species work, both list Human, Mouse, Rat reactivity, while the supplied tissue image demonstrates only human tonsil staining with PB9102 (catalog: M00799-2, PB9102; PB9102 IHC caption).
Each figure is that product's own IHC / IF validation image from its datasheet.
References
- UniProt Consortium. UniProt entry P41240 (CSK_HUMAN, Tyrosine-protein kinase CSK).
- Human Protein Atlas. CSK tissue IHC expression (reliability: Approved).
- Human Protein Atlas. CSK subcellular location (ICC-IF): Localized to vesicles and cytosol..
- Human Protein Atlas. CSK antibody validation summary (3 antibodies).
- Estrogen-regulated feedback loop limits the efficacy of estrogen receptor-targeted breast cancer therapy. Proceedings of the National Academy of Sciences of the United States of America 2018 — PMC6077722.
- Oncogenic Ras/Src cooperativity in pancreatic neoplasia. Oncogene 2011 — PMC3104672.
- An immunometabolism-related signature for renal clear cell carcinoma diagnosis and therapeutic target. Journal of cell communication and signaling 2025 — PMC12443813.
- Genetic associations of plasma proteins and breast cancer identify potential therapeutic drug candidates. Communications biology 2025 — PMC12000288.
- PubMed PMID:1945408 — UniProt-cited evidence.
- PubMed PMID:1720539 — UniProt-cited evidence.
- PubMed PMID:1371489 — UniProt-cited evidence.
Immunohistochemistry protocol sheet for CSK (Tyrosine-protein kinase CSK). Expected localisation Cytoplasmic tissue staining; a membrane pool is possible (HPA tissue IHC: cytoplasm; UniProt: membrane). Antigen retrieval: Citrate pH 6 HIER, heat-mediated (datasheet PB9102). Validated IHC antibody: PB9102 at 0.5-1μg/ml (the product's own IHC validation image is shown). Controls (HPA): positive Testis (Spermatogonia cells); negative Adipose tissue. IHC-P workflow on paraffin sections; fixative unspecified. Protocol steps: 1. Sample: Paraffin-embedded human tonsil tissues; fixative not specified (datasheet PB9102); 2. Fixation: Image fixative and duration unreported (datasheet PB9102); 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 PB9102); 6. Peroxidase block: 3% H2O2, 10 min , room temperature (standard); 7. Blocking: 10% goat serum (datasheet PB9102); 8. Primary antibody: Rabbit anti-CSK, 0.5-1μg/ml (datasheet PB9102); 9. Primary incubation: Overnight at 4 °C (datasheet PB9102). Watch for: Fixation: Keep fixation conditions consistent across sections. (standard IHC practice; not target-specific); Caveat: Antibody staining has low consistency with RNA expression (HPA tissue IHC); Isoform / epitope: No listed isoforms or extracellular domain (UniProt); Regulation: Tissue-dependent expression (HPA tissue IHC). Evidence: UniProt P41240, HPA tissue IHC · Approved, HPA ICC-IF · vesicles and cytosol., Datasheet PB9102, PMC6077722, PMC3104672. QR code links to https://www.bosterbio.com/bosterbio-gene-info-cards/CSK/immunohistochemistry-ihc-guide.