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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’s documented tonsil workflow and 1 μg/mL primary antibody (datasheet PB9102). Evaluate cytoplasmic staining by cell population while accounting for the reported low consistency between antibody staining and RNA expression (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 (HPA tissue IHC); membrane association is possible (UniProt) | |
| Staining pattern | Cytoplasmic signal in several tissues, including subsets of immune cells (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 consistent across sections. (standard IHC practice; not target-specific) | |
| Caveat | Antibody staining and RNA expression show low consistency (HPA tissue IHC) | |
| Regulation | Expression regulation is not specified (UniProt) | |
| Isoform / epitope | No reported isoforms or extracellular segment; epitope location remains relevant (UniProt) |
Section 1
Recommended CSK IHC & IF Protocols
The catalog antibody uses citrate pH 6 heat retrieval (datasheet: PB9102). The published CSK IHC protocols below cover breast and pancreatic tumor sections (PMC6077722; PMC3104672; PMC12000288).
| 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 citrate pH 6 retrieval for the catalog antibody (datasheet: PB9102); EDTA pH 9 is a published alternative for breast tumor sections (PMC6077722; PMC12000288).
Section 2
What Is the Expected CSK Staining Pattern?
CSK is mainly cytoplasmic, can associate with the cell membrane, and has no transmembrane segment (UniProt P41240 localisation and topology). In paraffin-section IHC, expect cytoplasmic staining in selected cells, particularly spermatogonia and subsets of immune cells (HPA: high in spermatogonia; cytoplasmic expression in subsets of immune cells). Interpret weak or unexpected staining cautiously: HPA rates tissue IHC Approved but reports low consistency between antibody staining and RNA expression (HPA tissue IHC).
| Distinct cytoplasmic signal in testicular spermatogonia; weaker signal in some lymph node cells. | This fits the observed cell distribution: spermatogonia stain High, while lymph node non-germinal center cells stain Medium (HPA tissue IHC). Score each cell population separately rather than treating the whole section as uniformly positive (standard IHC practice). |
| Strong, uniform nuclear staining dominates the candidate-positive cells. | That compartment conflicts with CSK's mainly cytoplasmic localisation (UniProt P41240 localisation) and the cytoplasmic tissue profile (HPA tissue IHC). Check whether the signal remains after omitting primary antibody; persistent colour suggests detection background (standard IHC practice). |
| Strong staining appears in adipocytes or heart cardiomyocytes. | Those cell populations are listed as Not detected (HPA tissue IHC). Treat the result as suspect and review cell identification, nonspecific antibody binding and endogenous chromogen-generating activity (standard IHC practice). HPA's low staining–RNA consistency limits certainty about any single negative population (HPA tissue IHC). |
| Colour spreads across stroma, lumina and multiple cell types without clear cytoplasmic boundaries. | This diffuse pattern is hard to assign to CSK-positive cells; HPA describes cytoplasmic expression in several tissues, including subsets of immune cells (HPA tissue IHC). Inspect a primary-omission control and compare the distribution with tissue structure (standard IHC practice). |
| No signal appears in spermatogonia in a testis control section. | The expected High staining is absent (HPA tissue IHC). First verify that spermatogonia are present and tissue morphology is preserved; then check primary-antibody application, the validated IHC workflow and detection reagents (standard IHC practice). One negative run cannot establish that CSK is absent. |
💡Expected CSK appearanceA convincing positive shows predominantly cytoplasmic colour in identifiable spermatogonia (High) or selected lymph node non-germinal center cells (Medium) (HPA tissue IHC; UniProt P41240 localisation), while dominant nuclear colour or indiscriminate staining across negative cell populations warrants investigation (standard IHC practice; HPA tissue IHC).
| Compartment and membrane recruitment | CSK is mainly cytoplasmic and can occur at the membrane, including lipid rafts (UniProt P41240 localisation). Interactions with membrane-associated partners recruit it there (UniProt P41240 subunit). Limited membrane-associated signal can fit this biology; a continuous membrane outline is not required by the reported tissue pattern (HPA tissue IHC). |
| Choice of comparison cell population | Spermatogonia provide a High observed signal; lymph node non-germinal center cells and duodenal glandular cells are Medium (HPA tissue IHC). Adipocytes and cardiomyocytes are listed as Not detected (HPA tissue IHC). Compare the named cells, not whole-organ averages. |
| Strength of IHC evidence | Three listed antibodies have IHC status Approved; none is listed as IHC Enhanced (HPA antibodies). HPA also reports low consistency between antibody staining and RNA expression (HPA tissue IHC). Use the reported pattern as a reference for interpretation, with that validation limit in view. |
| IHC versus ICC-IF readout | HPA reports enhanced vesicle and cytosol localisation by ICC-IF (HPA subcellular), while tissue IHC is described as cytoplasmic (HPA tissue IHC). These are different preparations and readouts; vesicle detail seen in cultured-cell IF need not be resolved in chromogenic paraffin sections (standard microscopy practice). |
| Situation | Likely cause | Next action |
|---|---|---|
| Testis control is blank, including identifiable spermatogonia. | A technical failure is plausible because spermatogonia are High in the HPA tissue IHC profile. | Confirm cell identity and section quality, then verify primary-antibody application and detection steps against the validated IHC workflow (standard IHC practice). Do not infer CSK absence from this run. |
| Signal is broadly nuclear. | Dominant nuclear staining disagrees with the cytoplasmic reference pattern (UniProt P41240 localisation; HPA tissue IHC). | Examine a primary-omission control and review the counterstain and chromogen distribution before assigning the nuclear colour to CSK (standard IHC practice). |
| Many expected-negative cells stain, including adipocytes. | Adipocytes are Not detected in the HPA tissue IHC profile; widespread colour may reflect nonspecific or endogenous signal (standard IHC practice). | Check a primary-omission control, inspect whether colour follows cell boundaries, and review blocking and detection controls (standard IHC practice). |
| Background obscures positive-cell boundaries. | Diffuse chromogen can prevent assessment of the reported cytoplasmic distribution (HPA tissue IHC; standard IHC practice). | Compare control sections and review antibody dilution, wash steps and detection development using the validated IHC workflow (standard IHC practice). |
| Staining is weak in a comparison tissue. | Expected levels differ by cell type: lymph node non-germinal center cells are Medium, while spermatogonia are High (HPA tissue IHC). | Score the specified cells and compare them with the testis control before changing the interpretation; allow for HPA's reported staining–RNA inconsistency (HPA tissue IHC). |
| Does IF/ICC need the same appearance as tissue IHC? | HPA describes enhanced vesicle and cytosol localisation in ICC-IF, and cytoplasmic expression in tissue IHC (HPA subcellular; HPA tissue IHC). | Assess the IF image for cytosolic and vesicular signal using its own readout; interpret paraffin-section chromogenic IHC by the tissue cell pattern (HPA subcellular; 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 score staining in spermatogonia (High; HPA: testis, spermatogonia). Use adipose tissue adipocytes as a negative tissue (HPA: adipocytes, Not detected); on the testis slide, compare spermatogonia with neighboring cell types and treat unstained cells as internal negatives only after confirming their identity (HPA: testis, spermatogonia High).
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 a no-primary secondary-only control, a concentration-matched nonimmune rabbit IgG control matched to the primary’s clonality where applicable, and a matched CSK-deficient sample or validated peptide-block control (PB9102 IHC caption: rabbit primary). For chromogenic detection, block endogenous peroxidase and check for endogenous biotin background because the documented testis-slide workflow uses biotinylated secondary antibody, avidin-biotin detection, and DAB (PB9102 IHC caption).
⚠️Feasibility: A target-specific fixation window or fixation effect is unreported, and the selected paraffin-section caption does not state a fixative (PB9102 IHC caption). The caption uses heat retrieval in citrate buffer at pH 6 for 20 minutes, but whether retrieval is required is unreported (PB9102 IHC caption). Frozen-section ease is unreported; ICC-IF images exist for A-431, U-251MG, U2OS, and HEK293 (HPA: subcellular), while testis scoring requires distinguishing spermatogonia from neighboring cells (HPA: testis, spermatogonia High).
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
Troubleshoot CSK staining in paraffin sections by checking retrieval, controls, cellular distribution, and scoring before interpreting chromogenic signal.
How should I retrieve CSK antigen when staining paraffin sections?
Start with heat-mediated citrate retrieval at pH 6 for 20 minutes (datasheet PB9102). The selected paraffin-section example used this treatment before overnight primary incubation at 4°C (datasheet PB9102). If staining is weak, compare a carefully titrated longer heating step or an alternative retrieval buffer on adjacent sections while keeping detection and imaging conditions fixed (standard IHC practice). Include a section processed without primary antibody to reveal retrieval-associated background, and check that tissue structure remains intact (standard IHC practice). Record the actual heating and cooling conditions, because changes in either can affect staining reproducibility (standard IHC practice).
Could fixation explain weak or uneven CSK staining?
The selected paraffin-section caption does not state its fixative, and target-specific CSK sensitivity to fixation is unknown (datasheet PB9102). Do not infer a preferred fixative from reported tissue staining or CSK’s cytoplasmic location (HPA tissue IHC; UniProt P41240 subcellular location). For a troubleshooting comparison, process matched sections with documented fixation duration, section thickness, and the same citrate retrieval at pH 6 for 20 minutes (datasheet PB9102; standard IHC practice). Compare morphology and CSK signal across the matched preparations, using a no-primary control to assess nonspecific detection (standard IHC practice). Treat any fixation effect as an observation from that comparison, not an established property of CSK (standard IHC practice).
Should CSK staining be cytoplasmic or membrane associated?
Expect predominantly cytoplasmic staining, with possible membrane-associated signal because CSK is mainly cytoplasmic and can occur in lipid rafts (UniProt P41240 subcellular location). CSK has no transmembrane segment, so a continuous membrane outline alone deserves scrutiny rather than automatic acceptance as target staining (UniProt P41240 topology; standard IHC practice). Its interactions with phosphorylated membrane-associated partners can recruit it near the plasma membrane (UniProt P41240 subunit and function). Compare suspected membrane enrichment with adjacent cytoplasmic staining and a no-primary control under identical chromogen development (standard IHC practice). HPA also reports cytoplasmic expression in several tissues, including subsets of immune cells (HPA tissue IHC profile).
How can epitope choice affect CSK interpretation?
The supplied record lists 0 isoforms, so avoid explaining discrepant staining by an undocumented CSK splice variant (UniProt P41240 isoforms). CSK contains SH3 residues 9–70, SH2 residues 82–171, and kinase residues 195–449 (UniProt P41240 domains). The selected caption does not identify the antibody’s epitope, so it cannot establish whether retrieval exposes a particular domain or modification-dependent site (datasheet PB9102). Document the mapped epitope if separately available, and compare independent antibody staining or an appropriate loss-of-target control before assigning a surprising pattern to CSK (standard IHC practice). Report phosphosite-specific interpretation only when the reagent has supporting specificity evidence; CSK has several annotated modified residues (UniProt P41240 modified residues; standard IHC practice).
How should I investigate CSK by multiplex immunofluorescence?
Use IF as a separate assay and multiplex CSK with a validated marker for the expected cell population, such as an immune-cell marker when examining immune-cell subsets (HPA tissue IHC profile; standard IF practice). Choose a CSK fluorophore in a channel with low measured tissue autofluorescence, and collect single-stain controls to assess spectral bleed-through (standard IF practice). Because CSK is mainly cytoplasmic and lacks a transmembrane segment, test gentle permeabilisation for access to intracellular epitopes (UniProt P41240 subcellular location and topology; standard IF practice). HPA reports vesicular and cytosolic IF localisation, but those observations do not establish the optimal permeabilisation conditions for this antibody (HPA subcellular profile; standard IF practice). Compare cellular distribution with the chromogenic result without treating fluorescence intensity as an equivalent DAB score (standard IHC/IF practice).
What should I check when CSK DAB staining is widespread?
Run a no-primary control through the same secondary and DAB steps to identify signal from the detection workflow (standard IHC practice). The selected example used 10% goat serum blocking, biotinylated goat anti-rabbit secondary antibody, and a streptavidin–biotin complex with DAB (datasheet PB9102). If background persists, assess endogenous peroxidase and biotin contributions with appropriate controls, and optimise blocking, washing, and primary concentration on adjacent sections (standard IHC practice). The example used 1 μg/ml primary antibody overnight at 4°C; treat that as a starting condition for this reagent, not proof of specificity in every specimen (datasheet PB9102; standard IHC practice). Interpret diffuse staining against the expected mainly cytoplasmic distribution (UniProt P41240 subcellular location).
How should I score CSK staining across tissue samples? ⚠ ANSWER MARKED FOR VERIFICATION
Define the cell population and scoring compartment before reviewing group labels, because CSK is mainly cytoplasmic and HPA reports staining in subsets of immune cells (UniProt P41240 subcellular location; HPA tissue IHC profile; standard IHC practice). For cytoplasmic DAB, record percentage of positive cells and intensity categories, then calculate an H-score if the categories are reproducible (standard IHC practice). For sparse positive populations, report positive-cell density per mm² of viable tissue or the fraction of cells positive within the annotated population (standard IHC practice). Normalise counts to the relevant cell population or viable tissue area, and keep retrieval, development, counterstaining, and image thresholds consistent across samples (standard IHC practice). Report background-control results alongside scores (standard IHC practice).
When is an apparent CSK-positive section convincing?
A convincing pattern places signal mainly in cytoplasm, with possible membrane enrichment, and agrees with an appropriate positive control (UniProt P41240 subcellular location; standard IHC practice). HPA reports high staining in spermatogonia and medium staining in lymph-node non-germinal-center cells, but describes low consistency between antibody staining and RNA expression data (HPA tissue IHC). Scrutinise isolated nuclear-only staining, strong tissue-edge staining, necrotic regions, and signal remaining in no-primary controls before calling a specimen positive (UniProt P41240 subcellular location; standard IHC practice). Endogenous peroxidase or biotin can confound a biotin-based DAB workflow, so check detection controls when the pattern is unexpected (datasheet PB9102; standard IHC practice). Confirm consequential findings with an independent specificity control and documented cell identity (standard IHC practice).
Boster reagents
Best CSK / Tyrosine-protein kinase CSK IHC Antibodies
PB9102 has real IHC data from a human paraffin section (PB9102 IHC caption); both antibodies list Human, Mouse and Rat reactivity, with no IF data supplied (catalog reactivity and image alts).
Real IHC data
Anti-Csk Antibody ®
Cat # PB9102
PB9102 will render with an IHC figure from paraffin-embedded human tonsil; its catalog lists Human, Mouse and Rat reactivity (PB9102 IHC caption; catalog reactivity). M00799-2 lists IHC and Human, Mouse and Rat reactivity, but has no IHC or IF image in the payload (M00799-2 catalog applications, reactivity and image alts).
Which to pick: Choose PB9102 for tissue IHC: its own caption documents human tonsil paraffin sections, citrate retrieval at pH 6 for 20 minutes, and 1 μg/ml primary antibody; the fixative is unreported (PB9102 IHC caption). For cross-species work, both SKUs list Human, Mouse and Rat reactivity, but the supplied tissue IHC figure demonstrates only human tissue; M00799-2 is rabbit monoclonal and has no supplied IHC figure (catalog reactivity and clone; PB9102 IHC caption; M00799-2 image alts). Neither SKU lists IF/ICC or supplies an IF figure, so there is no supported IF/ICC pick here (catalog applications and IF image alts).
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 (HPA tissue IHC); membrane association is possible (UniProt). 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 consistent across sections. (standard IHC practice; not target-specific); Caveat: Antibody staining and RNA expression show low consistency (HPA tissue IHC); Isoform / epitope: No reported isoforms or extracellular segment; epitope location remains relevant (UniProt); Regulation: Expression regulation is not specified (UniProt). 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.