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TK1 / Thymidine kinase, cytosolic · IHC design guide
Design Immunohistochemistry for TK1
Plan TK1 IHC-P around cytoplasmic staining in tonsil germinal center cells (HPA tissue IHC). The catalog antibody M04850-1 is shown on formaldehyde-fixed paraffin sections at 1:25 (datasheet M04850-1).
Evidence assembled Oct 2026 · For research use; verify linked source records and product datasheet before use
TK1 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) | |
| Staining pattern | Cytoplasmic signal in immune, squamous and glandular cells (HPA tissue IHC) | |
| Antigen retrieval | Citrate pH 6 HIER, heat-mediated (datasheet M04850-1) | |
| Positive control | Bone marrow+4 more · see all | |
| Negative control | Adipose tissue+4 more · see all |
Important caveats
Reasons your staining may differ from the expected pattern.
| Fixation | Use formaldehyde-fixed paraffin sections (selected-SKU IHC image M04850-1) | |
| Caveat | S-phase restriction can yield heterogeneous staining (UniProt) | |
| Regulation | Expression is limited to S phase (UniProt) | |
| Isoform / epitope | No isoforms annotated; mature chain spans residues 2–234 (UniProt) |
Section 1
Recommended TK1 IHC & IF Protocols
The catalog antibody’s IHC-P protocol is followed by three published TK1 IHC protocols, with each table limited to details reported in its article.
| Sample | Formaldehyde-fixed, paraffin-embedded human skeletal muscle tissue (datasheet M04850-1) |
| Fixation | Image formalin-fixed; duration unreported (datasheet M04850-1); verify before use. |
| Sectioning | 4–5 µm sections on charged slides (standard) |
| Deparaffinisation | Xylene, graded ethanol series to water (standard) |
| Antigen retrieval | Heat retrieval: Citrate pH 6 (datasheet M04850-1); 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 | Rabbit anti-TK1, 1:25 (datasheet M04850-1) |
| Primary incubation | 1 hours at 37°C (datasheet M04850-1) |
| Detection | HRP-polymer secondary, DAB chromogen 5–10 min (standard) |
| Counterstain | Hematoxylin, blue, dehydrate and mount (standard) |
| Expected result | TK1-positive staining in hematopoietic cells of bone marrow (HPA tissue IHC: High). HPA tissue profile: Cytoplasmic expression in immune cells, squamous epithelia and glandular cells of the female genital system, and in the gastrointestinal tract. No signal in the no-primary control. |
💡Decision noteStart with heat-mediated citrate retrieval at pH 6 (datasheet: M04850-1); one published TK1 protocol also specifies citrate at pH 6.0 (PMC6797230).
Section 2
What Is the Expected TK1 Staining Pattern?
TK1 is a cytoplasmic, cell-cycle-regulated enzyme with no transmembrane segment (UniProt P04183). In paraffin-section IHC, expect cytoplasmic staining in selected hematopoietic, germinal center, and glandular cells, with levels varying by tissue (HPA: tissue IHC). HPA rates its tissue staining evidence “Enhanced,” while describing medium consistency between antibody staining and RNA expression; use the listed cell patterns as guides rather than a promise that every cell will stain (HPA: tissue IHC).
| Discrete cytoplasmic chromogen in hematopoietic cells of bone marrow or germinal center cells of tonsil or lymph node (HPA: High in these cells). | This matches TK1’s cytoplasmic location and the reported high-staining cell populations (UniProt P04183; HPA: tissue IHC). Compare positive cells with neighboring cells on the same section; TK1 expression is cell-cycle regulated, so uniform staining is not required (UniProt P04183). |
| Cytoplasmic staining in rectal glandular cells is strong, while colon, appendix, or cervical glandular cells stain less strongly (HPA: High in rectum; Medium in colon, appendix, and cervix). | That ordering agrees with the reported tissue IHC levels (HPA: tissue IHC). Score the relevant cells and compartment rather than treating a whole-tissue average as the expected result (standard IHC interpretation practice). |
| Chromogen is predominantly nuclear, confined to cell borders, or deposited outside cells (slide observation). | Those locations conflict with the cytoplasmic annotation and absence of a transmembrane segment (UniProt P04183). Treat the result as suspect and review morphology, counterstain, and detection controls before calling it TK1 (standard IHC interpretation practice). |
| Prominent staining appears in adipocytes or cardiomyocytes while an expected positive control also stains (HPA: Not detected in adipocytes and cardiomyocytes). | The cell assignment conflicts with HPA’s reported pattern and may reflect nonspecific antibody binding or endogenous detection activity (HPA: tissue IHC; standard IHC practice). Check a no-primary control and confirm that chromogen is inside the identified cells (standard IHC practice). |
| Chromogen spreads across stroma, empty spaces, or most cells without a discernible cytoplasmic pattern (slide observation). | Diffuse deposition does not establish TK1 localisation (UniProt P04183: Cytoplasm). Compare the no-primary control and review blocking, washing, and chromogen development as general IHC background checks (standard IHC practice). |
💡Expected TK1 appearanceCall a result positive when clear cytoplasmic chromogen occurs in the expected cells, especially high-staining bone marrow hematopoietic or tonsillar germinal center cells; widespread nuclear, border-only, or extracellular color is suspect (UniProt P04183; HPA: tissue IHC).
| Cell population and tissue choice (HPA: tissue IHC). | Bone marrow hematopoietic cells, tonsillar and lymph-node germinal center cells, and rectal glandular cells are reported High; appendix, cervix, and colon glandular cells are Medium (HPA: tissue IHC). Use the named cells when judging a control, since nearby cell populations need not share their level (standard IHC interpretation practice). |
| Cell-cycle dependence (UniProt P04183). | TK1 expression is limited to S phase by transcriptional regulation, so a mixed population may show heterogeneous staining (UniProt P04183). Interpret a negative cell alongside tissue morphology and positive cells; a single unstained cell does not invalidate an otherwise plausible pattern (standard IHC interpretation practice). |
| Intracellular location and topology (UniProt P04183). | TK1 is annotated in the cytoplasm and has no transmembrane segment or signal peptide (UniProt P04183). These annotations support an intracellular cytoplasmic call; they do not supply an epitope location or establish an antigen-retrieval condition (UniProt P04183; standard IHC practice). |
| Strength of staining evidence (HPA: tissue IHC; antibody validation). | HPA reports tissue reliability as Enhanced but describes medium consistency with RNA expression; CAB004683 is also listed as IHC Enhanced (HPA: tissue IHC; antibody validation). These ratings support comparison with reported patterns, without establishing identical intensity in every section (HPA: tissue IHC; standard IHC interpretation practice). |
| IF/ICC: what location can this guide predict? (UniProt P04183; HPA: subcellular). | A cytoplasmic pattern is the location-based expectation from UniProt, but HPA supplies no main ICC-IF location or cell-line images here (UniProt P04183; HPA: subcellular). Assess IF/ICC staining with its own controls and guide; the tissue IHC levels do not validate an IF/ICC protocol (HPA: tissue IHC; standard IF practice). |
| Situation | Likely cause | Next action |
|---|---|---|
| No staining in bone marrow hematopoietic cells or tonsillar germinal center cells (HPA: High in these cells). | A failed staining run is possible when a reported high-staining population is blank; tissue morphology alone cannot identify the failed step (HPA: tissue IHC; standard IHC practice). | Check a known-positive section in the same run, then review antibody dilution, retrieval, detection reagents, and development against the applicable IHC procedure (standard IHC practice). |
| Only nuclei stain in a tissue with otherwise recognizable cell morphology (slide observation). | A nuclear-only pattern conflicts with the annotated cytoplasmic location (UniProt P04183). | Review the counterstain and no-primary control, then confirm cytoplasmic signal in a reported positive cell population before scoring TK1 (UniProt P04183; HPA: tissue IHC; standard IHC practice). |
| Adipocytes or cardiomyocytes stain prominently (HPA: Not detected in these cells). | The reported cell-level pattern is inconsistent with HPA and raises concern for nonspecific binding or endogenous detection activity (HPA: tissue IHC; standard IHC practice). | Confirm the cell identity and compare no-primary and detection controls; investigate background before accepting that staining as TK1 (standard IHC practice). |
| Color appears diffusely across tissue or outside cell boundaries (slide observation). | Diffuse color obscures the expected cytoplasmic localisation and may reflect general IHC background (UniProt P04183; standard IHC practice). | Compare a no-primary control, inspect washing and blocking steps, and review chromogen development while retaining a known-positive control (standard IHC practice). |
| A reported Medium population looks weaker than a reported High population (HPA: tissue IHC). | HPA assigns different cell-level staining categories; weaker glandular staining in colon, appendix, or cervix than in rectum can be consistent with those reports (HPA: tissue IHC). | Score the named cell population and intracellular pattern against the run’s positive control before changing assay conditions (HPA: tissue IHC; standard IHC interpretation practice). |
| A section shows a few plausible positive cells among many unstained cells (slide observation). | Heterogeneity can fit cell-cycle-regulated TK1 expression, although sparse staining alone cannot prove specificity (UniProt P04183; standard IHC interpretation practice). | Check that positive cells have cytoplasmic signal, occupy a reported population, and exceed no-primary background before recording the result (UniProt P04183; HPA: tissue IHC; standard IHC practice). |
Experiment evidence
IHC & IF images showing TK1 staining
M04850-1 · IHCM04850-1 staining TK1 in human skeletal muscle tissue sections by Immunohistochemistry (IHC-P -paraformaldehyde-fixed, paraffin-embedded sec
P04850 · IHCImmunohistochemistry analysis of paraffin-embedded human breast carcinoma, using TK (Phospho-Ser13) Antibody. The picture on the right is bl
HPA · Cerebral cortexHuman Protein Atlas IHC, Cerebral cortex. Source: https://www.proteinatlas.org/ENSG00000167900-TK1/tissue/cerebral+cortex#imid_2098920
HPA · ColonHuman Protein Atlas IHC, Colon. Source: https://www.proteinatlas.org/ENSG00000167900-TK1/tissue/colon#imid_2098846
HPA · LiverHuman Protein Atlas IHC, Liver. Source: https://www.proteinatlas.org/ENSG00000167900-TK1/tissue/liver#imid_2098863
HPA · KidneyHuman Protein Atlas IHC, Kidney. Source: https://www.proteinatlas.org/ENSG00000167900-TK1/tissue/kidney#imid_2098848
← swipe / scroll for more images →
Real IHC / IF data behind the staining-pattern expectations in this section.
Sample controls for TK1 IHC & IF
🧪Run tonsil first: germinal center cells should stain for TK1 (HPA: High in tonsil germinal center cells). Use adipose tissue as the negative, with adipocytes expected to lack detectable staining (HPA: Not detected in adipocytes); on the tonsil slide, assess cells outside germinal centers as candidate internal low-signal cells without assuming they are TK1-negative (HPA: staining reported for germinal center cells).
Positive control tissue: Bone marrow (Hematopoietic cells, 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 TK1; derive a cell-line control from the positive tissue's cell type (Hematopoietic cells) and confirm it by RNA or western blot first.
Technical controls: Include a no-primary, secondary-only control and an irrelevant immunoglobulin control matched to the primary antibody’s host species and, where applicable, isotype and clonality; a TK1 knockout sample is the preferred biological negative (standard IHC practice). Quench endogenous peroxidase and assess endogenous biotin when using the caption’s biotinylated secondary in tonsil (caption: biotinylated goat polyvalent secondary; standard IHC practice).
⚠️Feasibility: A target-specific fixation window or fixation effect is unreported, and the selected M04850-1 tissue-IHC caption does not establish a fixative (supplied caption metadata: fixative not stated). Heat-mediated citrate retrieval at pH 6 is reported for the paraffin-section example, but whether retrieval is required for TK1 is unreported (M04850-1 caption: citrate buffer, pH 6). The supplied evidence does not establish that frozen sections or IF are easier (HPA subcellular: no ICC-IF cell-line images); in tonsil, check immune-cell peroxidase background and biotin-related signal when interpreting chromogenic staining (standard IHC practice; M04850-1 caption: biotinylated secondary).
HPA tissue IHC evidence for TK1
Comprehensive Human Protein Atlas IHC scoring per tissue (reliability: Enhanced — Medium 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 |
|---|---|---|---|---|
| Bone marrow | Hematopoietic cells | High | Protein (IHC) | HPA → |
| Lymph node | Germinal center cells | High | Protein (IHC) | HPA → |
| Rectum | Glandular cells | High | Protein (IHC) | HPA → |
| Skin | Melanocytes | High | Protein (IHC) | HPA → |
| Tonsil | Germinal center cells | High | Protein (IHC) | HPA → |
Undetected expression · recommended negative controls
| Tissue | Cell type | Level | Evidence | Source |
|---|---|---|---|---|
| Adipose tissue | Adipocytes | Not detected | Protein (IHC) | HPA → |
| Bronchus | Basal cells | Not detected | Protein (IHC) | HPA → |
| Caudate | Glial cells | Not detected | Protein (IHC) | HPA → |
| Cerebellum | Cells in granular layer | Not detected | Protein (IHC) | HPA → |
| Cerebral cortex | Glial cells | Not detected | Protein (IHC) | HPA → |
Section 3
Advanced TK1 IHC Tips
Troubleshoot TK1 staining in chromogenic IHC of paraffin sections using the catalog antibody’s tissue evidence and expected cytoplasmic localisation.
Which retrieval conditions should I start with for TK1 in paraffin sections?
Start with heat-mediated citrate buffer at pH 6 for TK1 paraffin sections (datasheet M04850-1). The selected tissue-IHC example used this retrieval before primary antibody at 1:25 for 1 hour at 37°C (M04850-1 tissue-IHC caption). If staining is weak, compare heating durations on adjacent sections while holding antibody concentration and detection chemistry constant (standard IHC practice). Use tissue with documented TK1 expression, such as tonsil germinal center cells, to judge whether retrieval improved signal (HPA: High in tonsil germinal center cells). Check for tissue damage and rising background alongside signal before adopting a longer heating step (standard IHC practice).
How should I investigate TK1 staining that varies between fixed specimens?
TK1-specific sensitivity to fixation is unknown from the supplied evidence; do not infer it from tissue expression or protein features. Record fixative, fixation duration, section thickness, and time in storage for each specimen before comparing staining (standard IHC practice). Run adjacent sections through the same citrate pH 6 retrieval and detection conditions to isolate variation introduced before staining (datasheet M04850-1; standard IHC practice). Include a concurrently processed positive control, such as tonsil germinal center cells, when assessing a weak run (HPA: High in tonsil germinal center cells; standard IHC practice). Interpret differences across fixation groups cautiously until matched specimens establish reproducibility (standard IHC practice).
What staining pattern supports specific TK1 detection?
Score cytoplasmic staining as the expected TK1 pattern in paraffin sections (UniProt P04183: Cytoplasm; HPA: cytoplasmic tissue expression). TK1 has no transmembrane segment, so a membrane-only outline warrants review of morphology, detection controls, and antibody specificity (UniProt P04183 topology; standard IHC practice). Examine hematopoietic cells in bone marrow or germinal center cells in tonsil as expression controls (HPA: High in bone marrow hematopoietic cells and tonsil germinal center cells). Compare their signal with an appropriate negative control section stained in the same run (standard IHC practice). Do not call isolated nuclear or extracellular deposits TK1 solely because they appear dark (UniProt P04183: Cytoplasm; standard IHC practice).
Could an isoform or modified epitope explain inconsistent TK1 staining?
No TK1 isoforms are annotated in the supplied record, so an isoform-specific explanation lacks support here (UniProt P04183: 0 annotated isoforms). The record lists modifications at Ser-2, Ser-13, and Ser-231, but the catalog antibody’s epitope is not supplied (UniProt P04183 modified residues; supplied antibody evidence). Do not attribute weak or uneven staining to one of these modifications without epitope mapping or direct testing (standard IHC interpretation). Compare adjacent sections with fixed retrieval and detection settings, then assess whether changes reproduce in a positive control (standard IHC practice). If specificity remains uncertain, seek an independently validated antibody with a documented epitope (standard IHC practice).
How can I check TK1 by IF alongside the chromogenic IHC result?
Treat IF as a separate validation experiment: the supplied catalog evidence documents tissue IHC, with no IF validation provided (M04850-1 tissue-IHC caption; supplied antibody evidence). Multiplex TK1 with a validated marker for the expected cell population, such as germinal center cells in tonsil, and compare cell identities with adjacent IHC sections (HPA: High in tonsil germinal center cells; standard IF practice). Choose a fluorophore channel after measuring unstained tissue autofluorescence, and include single-label controls for channel separation (standard IF practice). TK1 is cytoplasmic and has no transmembrane segment, so assess permeabilisation for access to its intracellular epitope (UniProt P04183 localisation and topology; standard IF practice). Do not transfer the IHC antibody dilution directly to IF (M04850-1 tissue-IHC caption; standard IF practice).
What should I check when TK1 chromogenic staining is diffuse?
First compare the stained section with a no-primary control to identify signal arising from detection reagents or tissue (standard IHC practice). For peroxidase-based detection, assess endogenous peroxidase blocking and inspect pigment or precipitate before changing the primary dilution (standard IHC practice). The selected example used 3% BSA for 0.5 hour and primary antibody at 1:25 for 1 hour at 37°C (M04850-1 tissue-IHC caption). If background persists, compare a dilution series while keeping retrieval, washes, and chromogen development consistent (standard IHC practice). Preserve recognisable cytoplasmic staining in an expression control when choosing the final conditions (UniProt P04183: Cytoplasm; HPA: High in tonsil germinal center cells).
How should I quantify TK1 staining across tissue sections? ⚠ ANSWER MARKED FOR VERIFICATION
Define the cell population and scoring area before measuring TK1, then exclude folds, necrosis, and section edges consistently (standard IHC practice). Report the percentage of positive cells and an H-score when staining intensity matters; state the intensity bins and denominator used (standard IHC practice). For scattered positive cells, report density per mm² of evaluable tissue or the relevant cell compartment (standard IHC practice). Normalise counts to the number of eligible cells, or density to measured tissue area, rather than comparing raw positive counts across unequal sections (standard IHC practice). Keep retrieval, detection, counterstain, and scoring thresholds constant across specimens (standard IHC practice).
How do I distinguish genuine TK1 positivity from staining artefacts?
A credible TK1 result places signal in cytoplasm and in cells consistent with the sampled tissue’s expression profile (UniProt P04183: Cytoplasm; HPA tissue IHC profile). Germinal center cells in tonsil provide a documented high-expression reference, whereas adipocytes are listed as not detected (HPA: tonsil germinal center cells High; adipose adipocytes Not detected). Treat nuclear-only, membrane-only, or extracellular staining as a specificity concern until controls resolve it (UniProt P04183 localisation and topology; standard IHC practice). Review section edges and necrotic regions for nonspecific deposits, and use a no-primary control to assess endogenous enzyme or detection background (standard IHC practice). Relate heterogeneous positivity to the cell-cycle context cautiously (UniProt P04183: S-phase-regulated expression).
Boster reagents
Best TK1 / Thymidine kinase, cytosolic IHC Antibodies
Two catalog antibodies have real IHC images from human tissue: skeletal muscle for M04850-1 and breast carcinoma for P04850 (catalog image captions). IF/ICC is listed for P04850, with no IF image supplied (catalog applications/images).
Real IHC data
Anti-TK1 Antibody (Center)
Cat # M04850-1
Real IHC data
Anti-Phospho TK (Ser13) Antibody
Cat # P04850
M04850-1 shows IHC-P staining in formaldehyde-fixed, paraffin-embedded human skeletal muscle (M04850-1 image caption). P04850 shows IHC staining in paraffin-embedded human breast carcinoma, with phospho-peptide blocking shown; its fixative is unreported (P04850 image caption).
Which to pick: For human tissue IHC-P, choose M04850-1 when a documented fixation and retrieval example is useful: its caption reports formaldehyde fixation and heat retrieval in citrate buffer at pH 6 (M04850-1 image caption). For IF/ICC, M04850 offers a human-reactive rabbit monoclonal option, while P04850 offers a rabbit polyclonal option listed for human, mouse, pig and rat (catalog applications, host and reactivity). For cross-species IHC, consider P04850 if phospho-Ser13 TK1 is the target; its image documents paraffin sections but does not report the fixative (P04850 title, reactivity and image caption).
Each figure is that product's own IHC / IF validation image from its datasheet.
References
- UniProt Consortium. UniProt entry P04183 (KITH_HUMAN, Thymidine kinase, cytosolic).
- Human Protein Atlas. TK1 tissue IHC expression (reliability: Enhanced).
- Human Protein Atlas. TK1 subcellular location (ICC-IF): Variation in transcript expression is correlated to the cell cycle..
- Human Protein Atlas. TK1 antibody validation summary (1 antibodies).
- Immunohistochemistry for Thymidine Kinase-1 (TK1): A Potential Tool for the Prognostic Stratification of Breast Cancer Patients. Journal of clinical medicine 2021 — PMC8623797.
- Loss of thymidine kinase 1 inhibits lung cancer growth and metastatic attributes by reducing GDF15 expression. PLoS genetics 2019 — PMC6797230.
- Nuclear TK1 expression is an independent prognostic factor for survival in pre-malignant and malignant lesions of the cervix. BMC cancer 2013 — PMC3665464.
- Expression Profile of Thymidine Kinase Genes in Cervical Squamous Cell Carcinoma Confirmed by Various Detection Methods. World journal of oncology 2025 — PMC11750753.
- PubMed PMID:6549046 — UniProt-cited evidence.
- PubMed PMID:3301530 — UniProt-cited evidence.
- PubMed PMID:14702039 — UniProt-cited evidence.
Immunohistochemistry protocol sheet for TK1 (Thymidine kinase, cytosolic). Expected localisation Cytoplasmic tissue staining (HPA tissue IHC). Antigen retrieval: Citrate pH 6 HIER, heat-mediated (datasheet M04850-1). Validated IHC antibody: M04850-1 at 1:25 (the product's own IHC validation image is shown). Controls (HPA): positive Bone marrow (Hematopoietic cells); negative Adipose tissue. IHC-P workflow on paraffin sections. Protocol steps: 1. Sample: Formaldehyde-fixed, paraffin-embedded human skeletal muscle tissue (datasheet M04850-1); 2. Fixation: Image formalin-fixed; duration unreported (datasheet M04850-1); verify before use.; 3. Sectioning: 4–5 µm sections on charged slides (standard); 4. Deparaffinisation: Xylene, graded ethanol series to water (standard); 5. Antigen retrieval: Heat retrieval: Citrate pH 6 (datasheet M04850-1); 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: Rabbit anti-TK1, 1:25 (datasheet M04850-1); 9. Primary incubation: 1 hours at 37°C (datasheet M04850-1). Watch for: Fixation: Use formaldehyde-fixed paraffin sections (selected-SKU IHC image M04850-1); Caveat: S-phase restriction can yield heterogeneous staining (UniProt); Isoform / epitope: No isoforms annotated; mature chain spans residues 2–234 (UniProt); Regulation: Expression is limited to S phase (UniProt). Evidence: UniProt P04183, HPA tissue IHC · Enhanced, HPA cell-line RNA · Variation in transcript expression is correlated to the cell cycle., Datasheet M04850-1, PMC8623797, PMC6797230. QR code links to https://www.bosterbio.com/bosterbio-gene-info-cards/TK1/immunohistochemistry-ihc-guide.