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FGG / Fibrinogen gamma chain · IHC design guide
Design Immunohistochemistry for FGG
FGG is a secreted protein detected in blood plasma (UniProt). This paraffin-section IHC guide uses selective plasma positivity and high staining at kidney proximal-tubule microvilli to help plan staining and interpretation (HPA tissue IHC).
Evidence assembled Oct 2026 · For research use; verify linked source records and product datasheet before use
FGG 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 | Selective positivity in plasma (HPA tissue IHC) | |
| Staining pattern | Plasma positivity; high at proximal-tubule microvilli (HPA tissue IHC) | |
| Antigen retrieval | Citrate pH 6 HIER, heat-mediated (datasheet A00790-1) | |
| Positive control | Kidney | |
| Negative control | Adipose tissue+4 more · see all |
Important caveats
Reasons your staining may differ from the expected pattern.
| Fixation | Matched tissue-IHC evidence does not establish the fixation claim. Validate the specimen-specific method before use. (selected-SKU IHC image A00790-1) | |
| Caveat | Plasma staining may reflect circulating FGG (UniProt) | |
| Regulation | Liver-enriched RNA (HPA tissue RNA) | |
| Isoform / epitope | 2 isoforms, Gamma-A and Gamma-B; epitope effects unclear (UniProt) |
Section 1
Recommended FGG IHC & IF Protocols
The catalog antibody protocol is followed by published IHC protocols for human HCC specimens (PMC6389006) and human lung tissue (PMC8756227).
| Sample | Paraffin-embedded human liver cancer tissues; fixative not specified (datasheet A00790-1) |
| Fixation | Image fixative and duration unreported (datasheet A00790-1); 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, 20 min (datasheet A00790-1) |
| Peroxidase block | 3% H2O2, 10 min, room temperature (standard) |
| Blocking | 10% goat serum (datasheet A00790-1) |
| Primary antibody | Rabbit anti-FGG, 0.5-1μg/ml (datasheet A00790-1) |
| Primary incubation | Overnight at 4 °C (datasheet A00790-1) |
| Detection | Streptavidin-biotin complex (SABC), DAB chromogen (datasheet A00790-1) |
| Counterstain | Hematoxylin, blue, dehydrate and mount (standard) |
| Expected result | FGG-positive staining in proximal tubules (microvilli) of kidney (HPA tissue IHC: High). HPA tissue profile: Selective positivity in plasma. No signal in the no-primary control. |
💡Decision noteStart with citrate pH 6 heat retrieval (datasheet: A00790-1); the lung protocol also reports pH 6.0 citrate-phosphate retrieval (PMC8756227).
Section 2
What Is the Expected FGG Staining Pattern?
FGG is secreted, has no transmembrane segment, and is detected in blood plasma (UniProt P02679). In tissue IHC, expect selective plasma positivity and strong staining at kidney proximal tubule microvilli (HPA tissue IHC: Supported; proximal tubules High). The plasma pattern and cellular RNA need not coincide for a secreted protein (HPA tissue IHC: reliability description).
| Plasma is positive, with high staining at kidney proximal tubule microvilli (HPA tissue IHC). | This matches the reported IHC pattern (HPA tissue IHC: Supported). Microvillar signal alone does not show that proximal tubule cells synthesize FGG; FGG is secreted and detected in plasma (UniProt P02679). |
| Strong nuclear staining dominates instead of the reported plasma or microvillar pattern (HPA tissue IHC). | Treat this as a discordant result, not the expected FGG localization (UniProt P02679: secreted; HPA tissue IHC: selective plasma positivity). Check whether staining persists in a no-primary control (general IHC practice). |
| Adipocytes or adrenal glandular cells stain strongly (HPA tissue IHC: Not detected in these cells). | The result conflicts with the reported cell patterns and warrants checking antibody specificity or endogenous detection activity (HPA tissue IHC; general IHC practice). It does not, by itself, establish FGG expression. |
| Color spreads evenly across cells, stroma, and empty regions without a discernible pattern. | Consider nonspecific background or detection chemistry before scoring FGG (general IHC practice). Compare a no-primary control and reassess blocking, antibody concentration, washing, and chromogen development. |
| No signal appears in plasma or kidney proximal tubule microvilli (HPA tissue IHC: expected positive sites). | A negative result in these reference locations is inconclusive until the IHC run is checked (general IHC practice). Verify detection and counterstain, then review the catalog antibody's IHC-P instructions; no FGG-specific fixation effect is supplied. |
💡Expected FGG appearanceCall the IHC result consistent with FGG when plasma is positive and kidney proximal tubule microvilli show high signal (HPA tissue IHC: Supported); dominant nuclear staining or strong signal in reported negative cells is discordant (UniProt P02679: secreted; HPA tissue IHC).
| Secreted protein and circulating pool (UniProt P02679). | FGG is detected in blood plasma (UniProt P02679), while tissue IHC shows selective plasma positivity (HPA tissue IHC). Interpret deposited or luminal material in that context; staining alone cannot identify its cell of synthesis. |
| Tissue RNA versus protein location (HPA tissue IHC). | RNA is tissue enriched in liver, yet the supplied IHC profile highlights plasma and kidney proximal tubule microvilli (HPA tissue IHC). HPA cautions that RNA and protein locations may differ for a secreted variant. |
| Reported negative cell types (HPA tissue IHC). | Adipocytes, adrenal glandular cells, appendix glandular cells, and bone marrow hematopoietic cells are listed as Not detected (HPA tissue IHC). Use the stated cells, rather than every structure in those tissues, for comparison. |
| IF/ICC Q: What intracellular pattern is reported? | A: HPA ICC-IF reports mainly endoplasmic reticulum, with additional vesicles (HPA subcellular: approved). This intracellular observation is separate from the plasma-focused tissue IHC profile (HPA tissue IHC). |
| Antibody evidence and processing (HPA antibodies; UniProt P02679). | Three listed antibodies have Supported IHC status (HPA antibodies). FGG has a signal peptide at residues 1–26 and a mature chain at 27–453 (UniProt P02679); the payload does not identify the catalog antibody's epitope. |
| Situation | Likely cause | Next action |
|---|---|---|
| Expected plasma staining is absent (HPA tissue IHC). | The run may have failed, or the antibody and detection settings may be unsuitable (general IHC practice). The supplied sources do not identify an FGG-specific fixation sensitivity. | Review the catalog antibody's IHC-P instructions and run controls; confirm that counterstain or chromogen development has not obscured a weak signal (general IHC practice). |
| Kidney signal is absent while plasma stains (HPA tissue IHC: proximal tubule microvilli High). | The sections may lack clearly identifiable proximal tubules, or the expected microvillar pattern may be difficult to resolve (general IHC practice). Plasma positivity alone does not assess that cell pattern. | Identify proximal tubules morphologically and inspect their luminal border before scoring the result (general IHC practice); compare with HPA's reported microvillar location. |
| Strong nuclear color dominates the section. | The location is discordant with secreted FGG and the reported tissue IHC profile (UniProt P02679; HPA tissue IHC). Nonspecific antibody or detection staining is possible (general IHC practice). | Compare a no-primary control, inspect the counterstain, and reassess antibody concentration and detection conditions (general IHC practice). |
| Reported negative cell types appear strongly positive (HPA tissue IHC). | Cross-reactivity or endogenous detection activity may contribute (general IHC practice); HPA lists the specified adipocytes and adrenal glandular cells as Not detected. | Check cell identity, a no-primary control, and the detection system's endogenous activity control before assigning cell-specific FGG positivity (general IHC practice). |
| Uniform brown haze obscures the plasma and microvillar pattern. | Nonspecific background can prevent interpretation of the reported IHC locations (general IHC practice; HPA tissue IHC). | Review blocking, washing, antibody concentration, and chromogen development with appropriate controls (general IHC practice). |
| ICC-IF shows intracellular staining that seems unlike tissue IHC. | HPA reports endoplasmic reticulum and vesicles in ICC-IF, while tissue IHC shows selective plasma positivity (HPA subcellular; HPA tissue IHC). | Interpret each application against its own HPA pattern; do not score the ICC-IF localization as a required pattern in paraffin-section IHC. |
Experiment evidence
IHC & IF images showing FGG staining
A00790-1 · IHCIHC analysis of FGG using anti-FGG antibody (A00790-1). FGG was detected in paraffin-embedded section of human liver cancer tissues. Heat me
M00790-3 · IFIF analysis of FGG using anti-FGG antibody (M00790-3). FGG was detected in an immunocytochemical section of HEP3B cells. Enzyme antigen retr
HPA · Cerebral cortexHuman Protein Atlas IHC, Cerebral cortex. Source: https://www.proteinatlas.org/ENSG00000171557-FGG/tissue/cerebral+cortex#imid_21150619
HPA · DuodenumHuman Protein Atlas IHC, Duodenum. Source: https://www.proteinatlas.org/ENSG00000171557-FGG/tissue/duodenum#imid_21150552
HPA · ColonHuman Protein Atlas IHC, Colon. Source: https://www.proteinatlas.org/ENSG00000171557-FGG/tissue/colon#imid_21150553
HPA · LiverHuman Protein Atlas IHC, Liver. Source: https://www.proteinatlas.org/ENSG00000171557-FGG/tissue/liver#imid_21150546
HPA · ICC-IF A-549Human Protein Atlas immunofluorescence, A-549, antibody HPA011159; green = FGG, blue = nucleus, red = microtubules.
HPA · ICC-IF A-549Human Protein Atlas immunofluorescence, A-549, antibody HPA011159; green = FGG, blue = nucleus, red = microtubules.
← swipe / scroll for more images →
Real IHC / IF data behind the staining-pattern expectations in this section.
Sample controls for FGG IHC & IF
🧪Run kidney first; proximal tubule microvilli should stain (HPA: High in kidney proximal tubule microvilli). Use adipose tissue adipocytes as the negative tissue (HPA: Not detected in adipocytes), and assess unstained neighboring structures on the kidney slide as an internal background reference without assigning them an unreported negative cell identity (HPA: kidney row identifies proximal tubule microvilli only).
Positive control tissue: Kidney (Proximal tubules (microvilli), HPA High)
Negative control tissue: Adipose tissue (HPA Not detected)
ICC-IF cell lines (HPA subcellular resource): HPA ICC-IF images show FGG in A-549, Hep-G2, U2OS, with annotated localisation: Endoplasmic reticulum (approved) (HPA subcellular).
Technical controls: Include a no-primary, secondary-only control, a host-matched rabbit IgG isotype control, and a validated FGG knockout or peptide-block control (caption: rabbit primary antibody; standard IHC controls). Check endogenous biotin background in kidney when using the stated streptavidin–biotin detection system (caption: SABC with DAB; standard IHC practice).
⚠️Feasibility: A target-specific fixation window or fixation effect is unreported, and the selected SKU caption does not state a fixative (caption: fixative not stated). The documented paraffin-section method used citrate retrieval at pH 6 for 20 minutes; whether FGG staining depends on that retrieval step is unreported (caption: heat-mediated retrieval). Frozen sections or IF cannot be judged easier from the supplied evidence; interpret vascular or luminal signal cautiously because FGG is detected in blood plasma and is secreted, while kidney can show endogenous biotin background with the caption’s SABC detection (UniProt P02679: plasma detection and secreted; caption: SABC; standard IHC practice).
HPA tissue IHC evidence for FGG
Comprehensive Human Protein Atlas IHC scoring per tissue (reliability: Supported — At least one protein variant secreted, tissue location of RNA and protein might differ and correlation is complex.). 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 |
|---|---|---|---|---|
| Kidney | Proximal tubules (microvilli) | High | 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 FGG IHC Tips
Troubleshoot FGG staining by separating circulating protein deposition from cellular signal and by comparing like tissue compartments (UniProt P02679; HPA tissue IHC).
What retrieval should I try first for weak FGG staining in paraffin sections?
Start with heat-mediated citrate retrieval at pH 6 for 20 minutes on paraffin sections (datasheet A00790-1). Keep section thickness, heating, and cooling consistent across slides before changing retrieval conditions, because these steps affect staining comparisons (standard IHC practice). The documented detection used 1 µg/mL primary antibody overnight at 4°C; use that condition as a reference when assessing retrieval (caption A00790-1). Compare retrieved and unretrieved sections with matched controls, then examine tissue structure as well as signal (standard IHC practice). Because FGG is secreted and detected in plasma, vascular or extracellular staining alone does not establish cellular expression (UniProt P02679; HPA tissue IHC).
How should I evaluate fixation as a cause of variable FGG IHC signal?
The paraffin-section caption does not state a fixative, so target-specific fixation sensitivity is unknown (caption A00790-1). Record the actual fixative and fixation duration for each specimen, and compare similarly processed sections before attributing a signal difference to FGG abundance (standard IHC practice). Inspect morphology for poor preservation or excessive processing, and repeat the documented pH 6, 20-minute citrate retrieval consistently across the comparison (standard IHC practice; caption A00790-1). Include a matched negative reagent control to identify staining unrelated to the primary antibody (standard IHC practice). Do not infer fixation tolerance from kidney staining or from FGG topology and modifications (HPA tissue IHC; UniProt P02679).
Should FGG appear inside cells or in extracellular spaces on tissue IHC?
FGG is a secreted protein detected in blood plasma, so assess luminal and extracellular staining separately from cellular staining (UniProt P02679; HPA tissue IHC). HPA reports selective plasma positivity and high staining at kidney proximal-tubule microvilli; these observations do not establish synthesis by every stained cell (HPA tissue IHC). HPA subcellular imaging also reports endoplasmic-reticulum and vesicular localisation, consistent with examining intracellular signal in the appropriate context (HPA subcellular). Score each compartment separately and inspect adjacent morphology with the counterstain before assigning a cell as positive (standard IHC practice). Use matched control sections to test whether apparent cytoplasmic staining persists beyond vascular or surface deposits (standard IHC practice).
Could isoforms or epitope processing explain discordant FGG staining?
FGG has Gamma-A and Gamma-B isoforms, but the supplied antibody caption does not identify its epitope or establish isoform selectivity (UniProt P02679; caption A00790-1). The precursor has a signal peptide at residues 1–26, and the reported gamma chain spans 27–453; an undisclosed epitope cannot be assigned to either region (UniProt P02679). Reported glycosylation sites include residues 78 and 334, with additional phosphorylation and sulfation sites, but their effects on this antibody's staining are untested here (UniProt P02679; caption A00790-1). If results disagree across specimens or antibodies, request epitope information and compare staining under the same retrieval and detection conditions (standard IHC practice).
How can I investigate FGG localisation with multiplex IF?
Treat IF as a separate validation experiment: the supplied A00790-1 evidence documents paraffin-section chromogenic IHC, not an IF procedure (caption A00790-1). Pair FGG with a validated proximal-tubule marker when examining the kidney microvillar signal reported by HPA, while retaining a nuclear channel for cell assignment (HPA tissue IHC; standard IF practice). Select spectrally separated fluorophores and place the weaker signal in a channel with less measured tissue autofluorescence; assess unstained tissue in every channel (standard IF practice). For an intracellular endoplasmic-reticulum or vesicular epitope, test controlled permeabilisation, whereas accessible extracellular signal may require none; the antibody epitope is unspecified (HPA subcellular; caption A00790-1; standard IF practice).
How do I distinguish FGG signal from chromogenic background?
Start with a section lacking primary antibody and inspect vessels, damaged areas, and section edges before interpreting brown deposits (standard IHC practice). The documented method uses 10% goat serum, a biotinylated secondary, a streptavidin–biotin complex, and DAB (caption A00790-1). Apply an appropriate peroxidase block for DAB detection and check whether the biotin-based detection system contributes tissue background (standard IHC practice). Compare suspect staining with the counterstained tissue structure and with controls processed through the same detection steps (standard IHC practice). Because plasma is selectively positive for FGG, staining confined to blood-containing spaces can be real protein signal without indicating local cellular expression (HPA tissue IHC; UniProt P02679).
How should I score FGG when cellular and plasma staining coexist? ⚠ ANSWER MARKED FOR VERIFICATION
Define cellular, luminal, and extracellular regions before scoring, because HPA reports selective plasma positivity and kidney proximal-tubule microvillar staining (HPA tissue IHC). For a defined cell population, report the percentage positive and an H-score from 0–300 using staining intensity and the percentage at each intensity (standard IHC practice). For extracellular deposits, report stained area or integrated DAB density per mm² of viable tissue rather than forcing a cell-based score (standard IHC practice). Normalise each comparison to the same tissue compartment, viable area, acquisition settings, and staining batch, and document vascular content separately (standard IHC practice). Exclude folds and necrotic regions by a prespecified rule (standard IHC practice).
What would make an apparent FGG-positive cell or deposit unconvincing?
A convincing result should match tissue morphology, survive comparison with reagent controls, and be reproducible across similarly processed sections (standard IHC practice). Plasma or clot-associated staining is plausible for secreted FGG, but it does not by itself demonstrate production by adjacent cells (UniProt P02679; HPA tissue IHC). Interpret apparent kidney cellular signal against the reported proximal-tubule microvillar pattern, and examine unexpected nuclear staining cautiously because the supplied localisation evidence places FGG in secretory compartments and extracellular fluid (HPA tissue IHC; HPA subcellular; UniProt P02679). Edge-only deposits, necrotic pools, or signal retained without primary antibody warrant investigation of processing or endogenous detection background (standard IHC practice).
Boster reagents
Best FGG / Fibrinogen gamma chain IHC Antibodies
Validated anti-FGG data cover paraffin-section IHC in human liver cancer tissue (A00790-1 image caption) and IF/ICC in HEP3B cells (M00790-3 image caption).
Real IHC data
Anti-Fibrinogen gamma chain/FGG Antibody ®
Cat # A00790-1
Real IF data
Anti-FGG Antibody ® (monoclonal, 5H9)
Cat # M00790-3
A00790-1 will render with IHC data from a human liver cancer paraffin section (A00790-1 image caption). M00790-3 will render with IF/ICC data from HEP3B cells (M00790-3 image caption).
Which to pick: Choose A00790-1 for tissue IHC: it is a rabbit antibody listed for IHC, with a human paraffin-section example (A00790-1 catalog; A00790-1 image caption). Choose mouse monoclonal M00790-3 for human IF/ICC; its applications and HEP3B image support that choice (M00790-3 catalog; M00790-3 image caption). For mouse or rat samples, A00790-1 has listed reactivity, but its pictured IHC evidence is human paraffin tissue and the fixative is unreported (A00790-1 catalog; A00790-1 image caption).
Each figure is that product's own IHC / IF validation image from its datasheet.
References
- UniProt Consortium. UniProt entry P02679 (FIBG_HUMAN, Fibrinogen gamma chain).
- Human Protein Atlas. FGG tissue IHC expression (reliability: Supported).
- Human Protein Atlas. FGG subcellular location (ICC-IF): Mainly localized to the endoplasmic reticulum. In addition localized to vesicles..
- Human Protein Atlas. FGG antibody validation summary (4 antibodies).
- FGG promotes migration and invasion in hepatocellular carcinoma cells through activating epithelial to mesenchymal transition. Cancer management and research 2019 — PMC6389006.
- Identification of an Osteochondral Erosion Process in Gout Driven by Fibrinogen-Integrin Activation and Local MSU Crystallization. Advanced science (Weinheim, Baden-Wurttemberg, Germany) 2026 — PMC13360169.
- Integrated analysis reveals lung fibrinogen gamma chain as a biomarker for chronic obstructive pulmonary disease. Annals of translational medicine 2021 — PMC8756227.
- Visualization of Neutrophil Extracellular Traps and Fibrin Meshwork in Human Fibrinopurulent Inflammatory Lesions: I. Light Microscopic Study. Acta histochemica et cytochemica 2016 — PMC5011235.
- PubMed PMID:6688357 — UniProt-cited evidence.
- PubMed PMID:2990550 — UniProt-cited evidence.
- PubMed PMID:14702039 — UniProt-cited evidence.
Immunohistochemistry protocol sheet for FGG (Fibrinogen gamma chain). Expected localisation Selective positivity in plasma (HPA tissue IHC). Antigen retrieval: Citrate pH 6 HIER, heat-mediated (datasheet A00790-1). Validated IHC antibody: A00790-1 at 0.5-1μg/ml (the product's own IHC validation image is shown). Controls (HPA): positive Kidney (Proximal tubules (microvilli)); negative Adipose tissue. IHC-P workflow on paraffin sections; fixative unspecified. Protocol steps: 1. Sample: Paraffin-embedded human liver cancer tissues; fixative not specified (datasheet A00790-1); 2. Fixation: Image fixative and duration unreported (datasheet A00790-1); 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 , 20 min (datasheet A00790-1); 6. Peroxidase block: 3% H2O2, 10 min , room temperature (standard); 7. Blocking: 10% goat serum (datasheet A00790-1); 8. Primary antibody: Rabbit anti-FGG, 0.5-1μg/ml (datasheet A00790-1); 9. Primary incubation: Overnight at 4 °C (datasheet A00790-1). Watch for: Fixation: Matched tissue-IHC evidence does not establish the fixation claim. Validate the specimen-specific method before use. (selected-SKU IHC image A00790-1); Caveat: Plasma staining may reflect circulating FGG (UniProt); Isoform / epitope: 2 isoforms, Gamma-A and Gamma-B; epitope effects unclear (UniProt); Regulation: Liver-enriched RNA (HPA tissue RNA). Evidence: UniProt P02679, HPA tissue IHC · Supported, HPA ICC-IF · Mainly localized to the endoplasmic reticulum. In addition localized…, Datasheet A00790-1, PMC6389006, PMC8756227. QR code links to https://www.bosterbio.com/bosterbio-gene-info-cards/FGG/immunohistochemistry-ihc-guide.