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C1QC / Complement C1q subcomponent subunit C · IHC design guide
Design Immunohistochemistry for C1QC
Plan C1QC staining in paraffin sections around mainly plasma positivity, with medium staining reported in selected glandular and stromal cells (HPA tissue IHC). This guide covers fixation, controls, chromogenic detection and interpretation of a secreted protein (UniProt).
Evidence assembled Oct 2026 · For research use; verify linked source records and product datasheet before use
C1QC 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 | Mainly plasma positivity (HPA tissue IHC) | |
| Staining pattern | Mainly plasma; some glandular and stromal cells stain (HPA tissue IHC) | |
| Antigen retrieval | Citrate pH 6.0 HIER, 95–98 °C, 20 min (rule: cytoplasmic / membrane antigen) | |
| Positive control | Colon+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 formalin fixation consistent across paraffin sections. (standard IHC practice; not target-specific) | |
| Caveat | Secreted C1QC may stain away from its source cells (UniProt) | |
| Regulation | Staining regulation is not annotated (UniProt) | |
| Isoform / epitope | No isoforms; mature C1QC lacks signal peptide 1–28 (UniProt) |
Section 1
Recommended C1QC IHC & IF Protocols
The catalog antibody’s IHC-P protocol is accompanied by four published C1QC chromogenic IHC workflows (PMC9589315; PMC11556279; PMC11880100; PMC8790889).
| Sample | Paraffin-embedded human lung carcinoma tissue; fixative not specified (datasheet A05666-1) |
| Fixation | Image fixative and duration unreported (datasheet A05666-1); verify before use. |
| Sectioning | 4–5 µm sections on charged slides (standard) |
| Deparaffinisation | Xylene, graded ethanol series to water (standard) |
| Antigen retrieval | Heat-induced epitope retrieval in citrate buffer, pH 6.0, 20 min at 95–98 °C (standard rule: cytoplasmic / membrane antigen) |
| 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-C1QC, 1:100 - 1:300 (datasheet A05666-1) |
| Primary incubation | Overnight at 4 °C (standard) |
| Detection | HRP-polymer secondary, DAB chromogen 5–10 min (standard) |
| Counterstain | Hematoxylin, blue, dehydrate and mount (standard) |
| Expected result | C1QC-positive staining in glandular cells of colon (HPA tissue IHC: Medium). HPA tissue profile: Mainly plasma positivity. No signal in the no-primary control. |
💡Decision noteStart with citrate pH 6.0 retrieval at 95–98 °C for 20 min (page retrieval setting); adjust against the published tissue workflows.
Section 2
What Is the Expected C1QC Staining Pattern?
C1QC is secreted and can bind antigen–antibody complexes at surfaces; it has no transmembrane segment (UniProt P02747). In paraffin sections, expect mainly plasma or extracellular positivity, with medium staining reported in selected glandular and stromal cells (HPA tissue IHC). Interpret those cell signals cautiously: HPA rates the tissue profile Supported and reports low agreement between staining and RNA expression, partly because secreted protein can appear away from its site of production (HPA tissue IHC).
| Plasma-dominant staining, with medium signal in colon or fallopian tube glandular cells. | This fits the observed tissue profile (HPA tissue IHC: mainly plasma positivity; Medium in the named glandular cells). Record extracellular and cell-associated signal separately: secreted C1QC may accumulate away from its producing cell (UniProt P02747; HPA reliability note). |
| Strong, sharply nuclear staining dominates the section. | A nuclear pattern conflicts with the reported secreted and cell-surface locations (UniProt P02747; HPA subcellular: Secreted). Treat it as suspect and assess the no-primary control and staining distribution before calling it C1QC (general IHC practice). |
| Prominent staining appears in adipocytes or cardiomyocytes. | These cells are reported Not detected in adipose tissue and heart muscle, respectively (HPA tissue IHC). Consider antibody cross-reactivity or endogenous detection activity; compare a no-primary control and an HPA-reported positive tissue under the same detection conditions (general IHC practice). |
| Uniform haze covers tissue, lumina and blank slide areas. | A widespread deposit is harder to reconcile with HPA’s mainly plasma-positive profile (HPA tissue IHC). Check the no-primary control, reagent background and wash quality before scoring it as extracellular C1QC (general IHC practice). |
| No signal appears in a section expected to be positive. | First confirm the expected compartment and cell type: HPA reports Medium glandular staining in colon and Medium stromal-cell staining in endometrium, but mainly plasma positivity overall (HPA tissue IHC). If both expected cell and plasma signals are absent, check controls and the IHC detection run (general IHC practice). |
💡Expected C1QC appearanceCall a positive when plasma or extracellular staining predominates, with up to Medium signal in HPA-reported glandular or stromal cells; isolated strong nuclear staining is suspect (HPA tissue IHC; UniProt P02747 topology).
| Secretion and tissue context | C1QC has a signal peptide at residues 1–28 and a mature chain at 29–245 (UniProt P02747). HPA reports mainly plasma positivity and warns that a secreted protein’s tissue staining may differ from its RNA location (HPA tissue IHC). Do not assign production to every stained cell. |
| Cell-surface association | C1QC participates in C1q binding to antigen-complexed IgG or IgM at pathogen surfaces, despite lacking a transmembrane segment (UniProt P02747). A surface-associated deposit can therefore fit its biology; a membrane-only pattern is not required for a positive call (UniProt P02747). |
| Antibody evidence | Two rabbit polyclonal antibodies, HPA001471 and CAB009828, have Supported IHC status (HPA antibodies). That status supports use of the reported staining as a reference, while HPA still notes low agreement between tissue staining and RNA expression (HPA tissue IHC). |
| Can ICC-IF establish a finer compartment? | HPA lists C1QC as Secreted but supplies no main intracellular location or ICC-IF image-bearing cell lines (HPA subcellular). This record cannot define an ICC-IF organelle pattern; assess IF/ICC using its separate guide rather than extrapolating an IHC protocol. |
| Situation | Likely cause | Next action |
|---|---|---|
| A positive-looking section has widespread brown haze. | Detection background may obscure HPA’s mainly plasma-positive pattern (HPA tissue IHC; general IHC practice). | Inspect a no-primary control, endogenous peroxidase blocking and wash quality; score only signal that remains distinguishable from background (general IHC practice). |
| The expected colon glandular-cell signal is absent. | The HPA observation is Medium, so the expected signal may be subtle; a failed detection run is another possibility (HPA tissue IHC; general IHC practice). | Compare the plasma compartment and a run control, then review the catalog antibody’s IHC-P conditions and detection steps (HPA tissue IHC; general IHC practice). |
| Adipocytes stain as strongly as the presumed positive area. | HPA reports adipocytes Not detected in adipose tissue; cross-reactivity or endogenous activity is possible (HPA tissue IHC; general IHC practice). | Check a no-primary control and compare distribution with an HPA-reported positive tissue; do not score adipocyte staining alone as validation (general IHC practice). |
| Only nuclei show crisp staining. | This conflicts with the secreted and cell-surface annotation, and HPA supplies no nuclear location (UniProt P02747; HPA subcellular). | Review counterstain and no-primary controls, then repeat with an IHC-supported antibody if needed (HPA antibodies; general IHC practice). |
| RNA-rich lymphoid tissue shows little local cellular stain. | HPA calls RNA tissue-enhanced in lymphoid tissue but describes mainly plasma positivity and low staining–RNA agreement (HPA tissue IHC). | Score the protein’s observed compartment independently of RNA abundance; use the HPA tissue image profile as the staining reference (HPA tissue IHC). |
| A granular cell-associated deposit is scored as proof of synthesis. | Secreted C1QC can be present away from its producing cell, and may associate with antigen–antibody complexes (HPA reliability note; UniProt P02747). | Report where the deposit sits without assigning its cellular source from IHC alone; distinguish cell-associated from plasma or extracellular signal (HPA tissue IHC; UniProt P02747). |
Experiment evidence
IHC & IF images showing C1QC staining
A05666-1 · IHCImmunohistochemistry analysis of paraffin-embedded human lung carcinoma tissue, using C1QC Antibody. The picture on the right is blocked wit
HPA · Cerebral cortexHuman Protein Atlas IHC, Cerebral cortex. Source: https://www.proteinatlas.org/ENSG00000159189-C1QC/tissue/cerebral+cortex#imid_531010
HPA · ColonHuman Protein Atlas IHC, Colon. Source: https://www.proteinatlas.org/ENSG00000159189-C1QC/tissue/colon#imid_530936
HPA · LiverHuman Protein Atlas IHC, Liver. Source: https://www.proteinatlas.org/ENSG00000159189-C1QC/tissue/liver#imid_530929
HPA · KidneyHuman Protein Atlas IHC, Kidney. Source: https://www.proteinatlas.org/ENSG00000159189-C1QC/tissue/kidney#imid_530930
← swipe / scroll for more images →
Real IHC / IF data behind the staining-pattern expectations in this section.
Sample controls for C1QC IHC & IF
🧪Run colon first and look for staining in glandular cells (Medium; HPA: colon); run adipose tissue as the negative comparator, focusing on adipocytes (HPA: not detected in adipocytes). On the colon slide, use cells without specific staining as an internal background reference, without assuming every nonglandular cell is C1QC-negative (HPA: colon glandular-cell staining).
Positive control tissue: Colon (Glandular cells, HPA Medium)
Negative control tissue: Adipose tissue (HPA Not detected)
ICC-IF cell lines (HPA subcellular resource): HPA carries no ICC-IF cell line for C1QC; derive a cell-line control from the positive tissue's cell type (Glandular cells) and confirm it by RNA or western blot first.
Technical controls: Include a no-primary (secondary-only) control and a control immunoglobulin matched to the primary antibody’s host species and class; for a polyclonal primary, use matched nonimmune IgG (standard IHC practice). A peptide-blocked section is a documented specificity control for the catalog antibody (A05666-1 tissue-IHC caption); quench endogenous peroxidase for chromogenic detection and block endogenous biotin if using biotin-based detection (standard IHC practice).
⚠️Feasibility: Paraffin-section IHC is documented, but the selected A05666-1 caption does not state the fixative; a target-specific fixation window and antigen-retrieval dependency are unreported in the supplied evidence (A05666-1 tissue-IHC caption). The supplied evidence does not establish whether frozen sections or IF are easier, and HPA lists no ICC-IF cell-line images (HPA: subcellular record). In colon, extracellular or cell-surface C1QC may complicate assignment of staining to a particular cell, so interpret signal with tissue morphology and controls (UniProt P02747: secreted; cell surface; HPA: colon glandular-cell staining).
HPA tissue IHC evidence for C1QC
Comprehensive Human Protein Atlas IHC scoring per tissue (reliability: Supported — Low consistency between antibody staining and RNA expression data. 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 |
|---|---|---|---|---|
| Colon | Glandular cells | Medium | Protein (IHC) | HPA → |
| Endometrium | Cells in endometrial stroma | Medium | Protein (IHC) | HPA → |
| Fallopian tube | Glandular cells | Medium | Protein (IHC) | HPA → |
| Gallbladder | Glandular cells | Medium | Protein (IHC) | HPA → |
| Prostate | 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 → |
| Breast | Adipocytes | Not detected | Protein (IHC) | HPA → |
| Caudate | Glial cells | Not detected | Protein (IHC) | HPA → |
| Cervix | Glandular cells | Not detected | Protein (IHC) | HPA → |
| Epididymis | Glandular cells | Not detected | Protein (IHC) | HPA → |
Section 3
Advanced C1QC IHC Tips
Troubleshoot C1QC staining in paraffin sections by checking retrieval, controls and where the signal appears before comparing samples.
How should I adjust retrieval if C1QC staining is weak or uneven?
Start with citrate pH 6.0 HIER at 95–98 °C for 20 min in paraffin sections (page retrieval rule). Keep section thickness, heating and cooling consistent across slides so differences in staining can be interpreted across samples (standard IHC practice). If staining remains weak, test a shorter or longer retrieval time on adjacent sections while watching for tissue damage and increased background (standard IHC practice). Only then consider an alternative buffer, such as EDTA pH 9, as a fallback requiring its own validation (standard IHC practice). Compare each condition with a no-primary control and the same detection settings (standard IHC practice).
Could fixation explain absent C1QC staining in paraffin sections?
C1QC-specific sensitivity to fixation is unknown from the supplied evidence; the selected paraffin-section caption does not state a fixative (selected-SKU caption: A05666-1). Record the fixative, fixation duration and tissue-processing history before comparing slides, because these variables can affect immunoreactivity in IHC (standard IHC practice). If a specimen stains poorly, compare sections from blocks with documented processing under the same retrieval and detection conditions (standard IHC practice). Avoid assigning a particular fixation effect to C1QC on the basis of its secreted location, collagen-like domain or modifications alone (UniProt P02747; standard IHC practice). Include a no-primary control when assessing diffuse background (standard IHC practice).
Where should C1QC signal appear in tissue IHC?
Assess C1QC as a secreted protein that can also associate with cell surfaces through immune complexes (UniProt P02747 subcellular annotation). The tissue-IHC profile is mainly plasma positivity, so diffuse extracellular signal can be biologically plausible and should not automatically be scored as cellular expression (HPA tissue IHC). Examine cell borders and surrounding material at higher magnification, then record extracellular and cell-associated staining separately (standard IHC practice). C1QC has no transmembrane segment, so a crisp membrane outline alone is insufficient to establish membrane insertion (UniProt P02747 topology). Use morphology and an adjacent cell-marker stain before attributing a deposit to a particular cell population (standard IHC practice).
How might C1QC processing and domains affect epitope detection?
C1QC has no annotated isoforms in this record, so do not explain discordant tissue staining by an assumed splice variant (UniProt P02747 isoforms). Its precursor contains a 1–28 signal peptide, whereas the annotated mature chain spans residues 29–245 (UniProt P02747 processing). The collagen-like region spans 31–112, the C1q domain spans 115–245, and glycosylation is annotated at residue 75 (UniProt P02747 domains and glycosylation). Ask which region the antibody recognizes when comparing reagents, because epitope accessibility can differ after processing or retrieval (standard IHC practice). Do not infer the catalog antibody’s exact epitope from staining alone; assess specificity with appropriate controls (standard IHC practice).
How can I adapt C1QC localisation checks to multiplex IF?
Treat IF as a separate assay requiring its own validation; the selected antibody evidence here is a paraffin-section IHC image with peptide blocking (selected-SKU caption: A05666-1). Pair C1QC with a validated marker for the cell population under study and inspect whether signal is cell-associated or extracellular (UniProt P02747 subcellular annotation; standard IF practice). Choose fluorophores in channels with low autofluorescence for the tissue, and include single-stain and no-primary controls to check bleed-through and background (standard IF practice). Because C1QC is secreted and has no transmembrane segment, establish whether the antibody recognizes accessible extracellular antigen before adding permeabilisation (UniProt P02747 topology and subcellular annotation). If intracellular antigen is the aim, optimise mild permeabilisation separately (standard IF practice).
What should I check when C1QC DAB staining looks diffuse?
First distinguish plausible extracellular C1QC from nonspecific haze: the protein is secreted, and the tissue-IHC profile reports mainly plasma positivity (UniProt P02747 subcellular annotation; HPA tissue IHC). Compare a no-primary slide with the test slide to reveal detection-system background, and verify that the peroxidase block is effective (standard chromogenic IHC practice). Titrate primary antibody and detection exposure on matched sections if both tissue and controls appear uniformly brown (standard IHC practice). Examine tissue folds, section edges and necrotic areas separately, because these features can accumulate misleading chromogen (standard IHC practice). The selected image includes peptide-blocking evidence, but it does not establish that every diffuse deposit is specific (selected-SKU caption: A05666-1).
How should I score C1QC when staining is extracellular? ⚠ ANSWER MARKED FOR VERIFICATION
Define the measurement compartment before scoring, because C1QC is secreted and the reported tissue-IHC pattern is mainly plasma positivity (UniProt P02747 subcellular annotation; HPA tissue IHC). For cell-associated signal, report the percentage of positive cells or an H-score using a consistent intensity scale and cell denominator (standard IHC quantification practice). For discrete extracellular deposits, measure stained area or deposit count per mm² of analyzable tissue instead (standard image-analysis practice). Normalize cell counts to the relevant cell population and deposit measurements to intact tissue area, excluding folds and necrosis by prespecified rules (standard IHC quantification practice). Keep threshold, illumination and DAB development comparable across the batch (standard IHC practice).
How can I distinguish genuine C1QC signal from IHC artefact?
A credible result should fit a secreted or cell-surface-associated protein, while allowing for extracellular staining (UniProt P02747 subcellular annotation). HPA reports mainly plasma positivity and low consistency between staining and RNA expression, so a mismatch with local RNA alone does not settle specificity (HPA tissue IHC reliability description). Check whether strong signal is confined to section edges, folds or necrosis, and compare with a no-primary slide for endogenous enzyme or detection background (standard chromogenic IHC practice). Review cell identity with morphology or an adjacent marker rather than assigning every positive deposit to its nearest cell (standard IHC practice). The selected paraffin-section image has a peptide-blocking comparison, which supports that image’s interpretation but does not validate every tissue pattern (selected-SKU caption: A05666-1).
Boster reagents
Best C1QC / Complement C1q subcomponent subunit C IHC Antibodies
A05666-1 has an IHC figure from a paraffin-embedded human lung carcinoma section (image caption). IF and ICC are listed applications, and Human, Mouse, and Rat are listed as reactive species (catalog).
Real IHC data
Anti-C1QC/Complement Component C1Qc Antibody
Cat # A05666-1
A05666-1 will render with its IHC figure from paraffin-embedded human lung carcinoma tissue, including a peptide-blocked comparison (image caption). The catalog lists IHC, IF, and ICC applications and Human, Mouse, and Rat reactivity; no IF figure is supplied (catalog).
Which to pick: For tissue IHC, choose A05666-1: its own image shows staining in a paraffin-embedded human lung carcinoma section; the fixative is unreported (image caption). For IF/ICC or work across Human, Mouse, and Rat, A05666-1 is the listed rabbit polyclonal option, but the supplied figure demonstrates human tissue IHC only (catalog: applications, reactivity, host, polyclonal; image caption).
Each figure is that product's own IHC / IF validation image from its datasheet.
References
- UniProt Consortium. UniProt entry P02747 (C1QC_HUMAN, Complement C1q subcomponent subunit C).
- Human Protein Atlas. C1QC tissue IHC expression (reliability: Supported).
- Human Protein Atlas. C1QC subcellular location (ICC-IF): Secreted.
- Human Protein Atlas. C1QC antibody validation summary (2 antibodies).
- Complement C1QC as a potential prognostic marker and therapeutic target in colon carcinoma based on single-cell RNA sequencing and immunohistochemical analysis. Bosnian journal of basic medical sciences 2022 — PMC9589315.
- Identification of hub genes in the crosstalk between type 2 diabetic nephropathy and obesity according to bioinformatics analysis. Adipocyte 2024 — PMC11556279.
- Identification of novel biomarkers for atherosclerosis using single-cell RNA sequencing and machine learning. Mammalian genome : official journal of the International Mammalian Genome Society 2025 — PMC11880100.
- High complement protein C1q levels in pulmonary fibrosis and non-small cell lung cancer associated with poor prognosis. BMC cancer 2022 — PMC8790889.
- PubMed PMID:1706597 — UniProt-cited evidence.
- PubMed PMID:14702039 — UniProt-cited evidence.
- PubMed PMID:16710414 — UniProt-cited evidence.
Immunohistochemistry protocol sheet for C1QC (Complement C1q subcomponent subunit C). Expected localisation Mainly plasma positivity (HPA tissue IHC). Antigen retrieval: Citrate pH 6.0 HIER, 95–98 °C, 20 min (rule: cytoplasmic / membrane antigen). Validated IHC antibody: A05666-1 at 1:100 - 1:300 (the product's own IHC validation image is shown). Controls (HPA): positive Colon (Glandular cells); negative Adipose tissue. IHC-P workflow on paraffin sections; fixative unspecified. Protocol steps: 1. Sample: Paraffin-embedded human lung carcinoma tissue; fixative not specified (datasheet A05666-1); 2. Fixation: Image fixative and duration unreported (datasheet A05666-1); 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-induced epitope retrieval in citrate buffer, pH 6.0 , 20 min at 95–98 °C…; 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-C1QC, 1:100 - 1:300 (datasheet A05666-1); 9. Primary incubation: Overnight at 4 °C (standard). Watch for: Fixation: Keep formalin fixation consistent across paraffin sections. (standard IHC practice; not target-specific); Caveat: Secreted C1QC may stain away from its source cells (UniProt); Isoform / epitope: No isoforms; mature C1QC lacks signal peptide 1–28 (UniProt); Regulation: Staining regulation is not annotated (UniProt). Evidence: UniProt P02747, HPA tissue IHC · Supported, HPA ICC-IF · Secreted, Datasheet A05666-1, PMC9589315, PMC11556279. QR code links to https://www.bosterbio.com/bosterbio-gene-info-cards/C1QC/immunohistochemistry-ihc-guide.