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CR1 / Complement receptor type 1 · IHC design guide
Design Immunohistochemistry for CR1
Plan CR1 chromogenic IHC on paraffin sections using the catalog antibody at 2–5 µg/mL (datasheet A01022-1). Score glomerular and lymphoid germinal-center staining (HPA tissue IHC), treating membrane localisation as a molecular expectation (UniProt).
Evidence assembled Oct 2026 · For research use; verify linked source records and product datasheet before use
CR1 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 | Membrane expected; tissue subcellular pattern unreported (UniProt; HPA tissue IHC) | |
| Staining pattern | Glomeruli and germinal centers; subcellular pattern unreported (HPA tissue IHC) | |
| Antigen retrieval | EDTA pH 8.0 HIER, heat-mediated (datasheet A01022-1) | |
| Positive control | Appendix+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 paraffin-section fixation consistent across specimens. (selected-SKU IHC image A01022-1) | |
| Caveat | Antibody staining may reflect products of multiple genes (HPA tissue IHC) | |
| Regulation | No tissue-staining regulator reported (UniProt; HPA tissue IHC) | |
| Isoform / epitope | No isoforms listed; extracellular versus cytoplasmic epitope matters (UniProt) |
Section 1
Recommended CR1 IHC & IF Protocols
The catalog antibody’s paraffin-section protocol (datasheet A01022-1) is accompanied by published chromogenic IHC methods using neocortex, mouse spleen, and mouse intestinal tissue (PMC6231989; PMC3707406; PMC4563784).
| Sample | Paraffin-embedded human endometrial carcinoma tissue; fixative not specified (datasheet A01022-1) |
| Fixation | Image fixative and duration unreported (datasheet A01022-1); verify before use. |
| Sectioning | 4–5 µm sections on charged slides (standard) |
| Deparaffinisation | Xylene, graded ethanol series to water (standard) |
| Antigen retrieval | Heat retrieval: EDTA pH 8.0 (datasheet A01022-1); 20 min, 95–100 °C (standard) |
| Peroxidase block | 3% H2O2, 10 min, room temperature (standard) |
| Blocking | 10% goat serum (datasheet A01022-1) |
| Primary antibody | Rabbit anti-CR1, 2-5μg/ml (datasheet A01022-1) |
| Primary incubation | Overnight at 4 °C (datasheet A01022-1) |
| Detection | HRP-conjugated secondary, DAB chromogen (datasheet A01022-1) |
| Counterstain | Hematoxylin, blue, dehydrate and mount (standard) |
| Expected result | CR1-positive staining in lymphoid tissue of appendix (HPA tissue IHC: Medium). HPA tissue profile: Highly selective expression in renal glomeruli, subsets of immune cells and follicular dendritic cells in lymphoid tissue. No signal in the no-primary control. |
💡Decision noteFor paraffin sections, start with heat-mediated EDTA pH 8.0 retrieval (datasheet A01022-1). The published mouse intestinal method used citrate pH 6.0 (PMC4563784).
Section 2
What Is the Expected CR1 Staining Pattern?
CR1 is a membrane receptor with a large extracellular region and one transmembrane segment (UniProt P17927 topology). In paraffin sections, expect staining in subsets of immune cells, follicular dendritic cells in lymphoid tissue, and cells in renal glomeruli (HPA tissue IHC). HPA rates the tissue pattern Enhanced but cautions that antibody staining may reflect proteins from more than one gene (HPA tissue IHC reliability).
| Cell outlines stain in renal glomeruli, lymphoid germinal centers, or splenic white pulp (HPA tissue IHC). | This supports the expected CR1 distribution when staining is confined to the relevant cells. HPA reports medium staining in glomerular cells, lymph node and tonsil germinal center cells, and splenic white pulp cells (HPA tissue IHC). Assess cell identity from the section; the glomerular cell subtype is unspecified in this record (HPA tissue IHC). |
| A nuclear or broadly cytoplasmic signal dominates cells that should show a membrane pattern (UniProt P17927 topology; HPA subcellular ICC-IF). | Treat the compartment mismatch as a possible artefact and review controls and detection background. CR1 is annotated as membrane localized, with residues 42–1971 extracellular and one transmembrane segment at 1972–1996 (UniProt P17927 topology). The supplied evidence does not establish a target-specific fixation effect. |
| Strong staining appears across adipocytes or respiratory epithelial cells (HPA tissue IHC). | These cell types are reported as not detected in adipose tissue and bronchus, respectively (HPA tissue IHC). Widespread signal there raises concern for cross-reactivity or endogenous detection activity. Check the stained cells, the negative control, and whether the signal follows the expected membrane distribution (UniProt P17927 topology). |
| A diffuse deposit covers many structures without clear cell outlines. | This is difficult to score as CR1 because the expected location is the cell membrane (UniProt P17927 topology; HPA subcellular ICC-IF). In general chromogenic IHC practice, review background in the negative control, blocking, reagent concentration, and wash steps before interpreting weak local staining. |
| No signal appears in an otherwise interpretable lymph node germinal center or renal glomerulus (HPA tissue IHC). | HPA reports medium staining in those compartments, so their absence calls for a technical review before calling the sample CR1 negative (HPA tissue IHC). Confirm that the expected cells are present and inspect the positive control, primary antibody, retrieval conditions, and detection run (general IHC practice). |
💡Expected CR1 appearanceCall a result positive when the appropriate glomerular or lymphoid cells show discernible, predominantly membrane associated chromogenic staining at the medium level reported by HPA; diffuse nuclear staining or broad staining of HPA negative cell types is suspect (HPA tissue IHC; UniProt P17927 topology).
| Cell and tissue selection | HPA reports medium staining in kidney glomerular cells, lymph node and tonsil germinal center cells, splenic white pulp cells, appendix lymphoid tissue, and bone marrow hematopoietic cells (HPA tissue IHC). These are useful positive comparison sites, but the record does not identify every stained cell subtype. |
| Topology and epitope location | CR1 has an extracellular region at residues 42–1971, a transmembrane region at 1972–1996, and a short cytoplasmic region at 1997–2039 (UniProt P17927 topology). Interpret compartmental staining in light of the antibody's documented epitope, if available; no antibody epitope is supplied here. |
| IHC antibody evidence | HPA lists Enhanced IHC validation for HPA042455, HPA043579, CAB002491, and CAB016271, and Supported IHC validation for HPA049348 (HPA antibodies). HPA also warns that staining may reflect proteins from more than one gene, so validation status alone does not resolve an unexpected cell pattern (HPA tissue IHC reliability). |
| Antigen retrieval | No CR1-specific retrieval condition or fixation sensitivity is supplied. Optimize retrieval with a known-positive tissue and its matched control as a general IHC workflow step; do not infer a CR1-specific retrieval requirement from the HPA staining levels or UniProt topology. |
| IF/ICC Q&A: Where should CR1 appear? | At the plasma membrane: HPA reports a supported plasma membrane location in ICC-IF and lists HEL among cell lines with ICC-IF images (HPA subcellular ICC-IF). This localization can inform interpretation, but the ICC-IF record does not establish an IHC retrieval setting or chromogenic staining intensity. |
| Situation | Likely cause | Next action |
|---|---|---|
| The positive-control germinal center or glomerulus is blank (HPA tissue IHC). | The expected cells may be absent from the section, or an IHC workflow step may have failed (general IHC practice). | Confirm the compartment on the counterstain, then review primary antibody, retrieval, and detection records; repeat with an appropriate positive control (general IHC practice). |
| Adipocytes or bronchial respiratory epithelium stain broadly (HPA tissue IHC). | Those cell types are listed as not detected; cross-reactivity or endogenous detection activity is possible (HPA tissue IHC; general IHC practice). | Compare with a matched negative control and inspect whether signal follows cell membranes. Review the detection system's background controls (UniProt P17927 topology; general IHC practice). |
| Nuclei dominate the stain. | The compartment conflicts with CR1 membrane localization (UniProt P17927 topology; HPA subcellular ICC-IF). | Check the negative control and counterstain, then reassess staining after background optimization before scoring cells as positive (general IHC practice). |
| Chromogen is diffuse across the section. | Background may obscure the cell outline needed to judge membrane localization (UniProt P17927 topology; general IHC practice). | Use the negative control to assess nonspecific deposit; review blocking, primary antibody concentration, washing, and detection conditions (general IHC practice). |
| A glomerulus stains, but its positive cell type is uncertain (HPA tissue IHC). | HPA specifies cells in glomeruli without assigning a finer cell identity (HPA tissue IHC). | Report the observed compartment and membrane pattern without naming a glomerular cell subtype; use morphology and appropriate cell markers if subtype assignment is required (general IHC practice). |
| Two antibodies give different cell patterns. | HPA's Enhanced reliability still carries a warning that staining may reflect proteins from more than one gene (HPA tissue IHC reliability). | Compare each pattern with HPA positive and negative cell types and with CR1 membrane localization; document the discrepancy before assigning CR1 positivity (HPA tissue IHC; UniProt P17927 topology). |
Experiment evidence
IHC & IF images showing CR1 staining
A01022-1 · IHCIHC analysis of CD35 using anti-CD35 antibody (A01022-1). CD35 was detected in a paraffin-embedded section of human endometrial carcinoma ti
A01022-1 · IHCIHC analysis of CD35 using anti-CD35 antibody (A01022-1). CD35 was detected in a paraffin-embedded section of human oesophagus squama cancer
HPA · Cerebral cortexHuman Protein Atlas IHC, Cerebral cortex. Source: https://www.proteinatlas.org/ENSG00000203710-CR1/tissue/cerebral+cortex#imid_14198108
HPA · ColonHuman Protein Atlas IHC, Colon. Source: https://www.proteinatlas.org/ENSG00000203710-CR1/tissue/colon#imid_14182202
HPA · LiverHuman Protein Atlas IHC, Liver. Source: https://www.proteinatlas.org/ENSG00000203710-CR1/tissue/liver#imid_14182203
HPA · KidneyHuman Protein Atlas IHC, Kidney. Source: https://www.proteinatlas.org/ENSG00000203710-CR1/tissue/kidney#imid_14182204
HPA · ICC-IF HELHuman Protein Atlas immunofluorescence, HEL, antibody HPA043579; green = CR1, blue = nucleus, red = microtubules.
HPA · ICC-IF HELHuman Protein Atlas immunofluorescence, HEL, antibody HPA043579; green = CR1, blue = nucleus, red = microtubules.
← swipe / scroll for more images →
Real IHC / IF data behind the staining-pattern expectations in this section.
Sample controls for CR1 IHC & IF
🧪Run lymph node first and score staining in germinal center cells (HPA: Medium in lymph node germinal center cells). Use adipose tissue adipocytes as the negative comparator (HPA: Not detected in adipocytes); on the positive slide, morphologically CR1-negative neighboring cells should remain at background, while cell identity should be checked before treating any lymphocyte as negative (UniProt P17927 tissue specificity).
Positive control tissue: Appendix (Lymphoid tissue, HPA Medium)
Negative control tissue: Adipose tissue (HPA Not detected)
ICC-IF cell lines (HPA subcellular resource): HPA ICC-IF images show CR1 in HEL, with annotated localisation: Plasma membrane (supported) (HPA subcellular).
Technical controls: Include a no-primary, secondary-only control and a host- and clonality-matched rabbit IgG isotype control for the caption’s rabbit primary (caption: rabbit anti-CD35); CR1-knockout material provides a biological negative if available. Block endogenous peroxidase for HRP/DAB detection and check blood-containing fields when scoring lymph node staining (caption: HRP/DAB; UniProt P17927 tissue specificity: erythrocytes).
⚠️Feasibility: A target-specific fixation window or fixation effect is unreported, and the selected A01022-1 tissue-IHC caption does not state its fixative (caption: fixative not stated). Heat retrieval in EDTA at pH 8.0 is a documented starting condition, but retrieval dependence is unreported (caption: EDTA pH 8.0). No matched evidence establishes frozen sections or IF as easier; CR1-positive erythrocytes and immune cells can complicate interpretation of lymph node staining (UniProt P17927 tissue specificity).
HPA tissue IHC evidence for CR1
Comprehensive Human Protein Atlas IHC scoring per tissue (reliability: Enhanced — Medium consistency between antibody staining and RNA expression data. Caution, targets protein from more than one gene.). 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 |
|---|---|---|---|---|
| Appendix | Lymphoid tissue | Medium | Protein (IHC) | HPA → |
| Bone marrow | Hematopoietic cells | Medium | Protein (IHC) | HPA → |
| Kidney | Cells in glomeruli | Medium | Protein (IHC) | HPA → |
| Lymph node | Germinal center cells | Medium | Protein (IHC) | HPA → |
| Spleen | Cells in white pulp | 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 → |
| Breast | Adipocytes | Not detected | Protein (IHC) | HPA → |
| Bronchus | Respiratory epithelial cells | Not detected | Protein (IHC) | HPA → |
| Caudate | Glial cells | Not detected | Protein (IHC) | HPA → |
Section 3
Advanced CR1 IHC Tips
Troubleshoot CR1 staining by checking retrieval, cell identity and membrane localisation before interpreting chromogenic signal (UniProt P17927; HPA tissue IHC).
Which retrieval conditions should I try first for weak CR1 staining in paraffin sections?
Start with heat-mediated antigen retrieval in EDTA at pH 8.0 (datasheet A01022-1). The selected product image used this condition to detect CD35 in a paraffin section of human endometrial carcinoma; its caption does not state the fixative (datasheet A01022-1). Keep retrieval conditions identical across study sections and run a positive-control section alongside them so changes in staining can be assessed consistently (standard IHC practice). If staining remains weak, optimise heating duration and cooling under controlled conditions before considering another retrieval buffer as a fallback (standard IHC practice). Assess whether signal resolves along cell surfaces, where CR1 is expected, rather than judging intensity alone (UniProt P17927 topology; HPA subcellular).
How should I troubleshoot variable CR1 staining between paraffin blocks?
The selected tissue-IHC caption reports a paraffin section but does not state its fixative, so target-specific fixation sensitivity is unknown (datasheet A01022-1). Record each block’s documented fixation and processing history, and compare sections processed as similarly as possible before changing antibody or retrieval conditions (standard IHC practice). Include the same positive-control section in each run to distinguish block-to-block variation from changes in staining performance (standard IHC practice). If a block stains weakly, repeat the documented EDTA pH 8.0 retrieval while keeping detection conditions constant (datasheet A01022-1; standard IHC practice). Do not infer a CR1-specific fixation effect from its tissue distribution or membrane topology (HPA tissue IHC; UniProt P17927 topology).
Where should convincing CR1 signal appear in tissue sections?
Prioritise staining along cell surfaces: CR1 is a membrane protein with an extracellular region at residues 42–1971 and a transmembrane segment at 1972–1996 (UniProt P17927 topology). Supported subcellular staining also places CR1 at the plasma membrane (HPA subcellular). Evaluate signal in the relevant tissue compartment, including renal glomeruli and lymphoid germinal-center or follicular dendritic-cell regions, rather than calling every stained cell positive (HPA tissue IHC). UniProt also reports CR1 on erythrocytes, mature B cells, monocytes, granulocytes and a subset of T cells, so cell identity matters (UniProt P17927 tissue specificity). Diffuse nuclear staining without a corresponding surface pattern warrants troubleshooting of background and detection (UniProt P17927 topology; standard IHC practice).
Could epitope location explain inconsistent CR1 staining?
First establish which CR1 sequence the catalog antibody recognises; no antibody epitope is specified in the supplied product caption (datasheet A01022-1). CR1 has a large extracellular region spanning residues 42–1971, a short cytoplasmic region at 1997–2039, and 30 annotated Sushi domains (UniProt P17927 topology and domains). Its extracellular sequence includes 20 annotated glycosylation sites, but their effect on this antibody’s staining has not been established by the supplied evidence (UniProt P17927 glycosylation; datasheet A01022-1). The supplied record lists 0 isoforms, so do not assign staining differences to a particular isoform from these data (UniProt P17927 isoforms). If results vary, compare retrieval and cell-surface patterns before proposing an epitope-based explanation (standard IHC practice; HPA subcellular).
How can I adapt the CR1 localisation question to multiplex IF?
For the separate IF/ICC workflow, pair CR1 with a validated marker that identifies the cell population under study; germinal-center and follicular dendritic-cell regions are relevant tissue contexts (HPA tissue IHC; standard IF practice). Choose fluorophores after inspecting unstained tissue for autofluorescence, and assign the cleaner detection channel to the weaker signal (standard IF practice). CR1 is expected at the plasma membrane, with residues 42–1971 extracellular and 1997–2039 cytoplasmic (HPA subcellular; UniProt P17927 topology). If the antibody recognises an extracellular epitope, minimise permeabilisation; if it recognises the cytoplasmic tail, optimise permeabilisation and verify that membrane outlines remain interpretable (UniProt P17927 topology; standard IF practice). The supplied caption establishes a chromogenic paraffin-section result, not IF validation for this antibody (datasheet A01022-1).
What should I check when CR1 staining appears widespread or diffuse?
Compare the distribution with expected CR1-rich compartments: renal glomeruli, subsets of immune cells and follicular dendritic cells in lymphoid tissue (HPA tissue IHC). Examine a no-primary control for detection background, and ensure the peroxidase-blocking step is effective before interpreting DAB deposits as antigen signal (standard IHC practice). The selected caption used 10% goat serum blocking, 2 μg/ml primary antibody overnight at 4°C, and a peroxidase-linked secondary before DAB development (datasheet A01022-1). If background persists, optimise blocking, washing and antibody concentration against a positive-control section while preserving the EDTA pH 8.0 retrieval reference condition (datasheet A01022-1; standard IHC practice). Score cellular membrane staining separately from diffuse extracellular colour or tissue-edge deposits (HPA subcellular; standard IHC practice).
How should I quantify CR1 staining across tissue sections? ⚠ ANSWER MARKED FOR VERIFICATION
Define the tissue compartment and eligible cell population before scoring; HPA reports selective signal in renal glomeruli and subsets of immune cells and follicular dendritic cells (HPA tissue IHC). For cell-based analysis, report the percentage of positive eligible cells and, when intensity is reproducible, an H-score spanning 0–300 (standard IHC practice). For spatially restricted populations, report CR1-positive cell density per mm² of the annotated compartment, with consistent exclusion of folds and damaged areas (standard IHC practice). Normalise cell counts to the number of eligible cells, or density to measured compartment area, rather than total section area when composition differs (standard IHC practice). Apply the same membrane-positivity threshold, controls and DAB acquisition settings across cases (HPA subcellular; standard IHC practice).
How can I distinguish genuine CR1 staining from artefact?
A credible result aligns cell-surface signal with a plausible CR1-bearing population; UniProt reports expression on erythrocytes, mature B cells, monocytes, granulocytes, follicular dendritic cells and a subset of T cells (UniProt P17927 tissue specificity and topology). Renal glomerular and lymphoid germinal-center staining have supporting tissue-IHC evidence, but the HPA record warns that its antibody staining can target protein from more than one gene (HPA tissue IHC). Treat isolated nuclear signal, tissue-edge enhancement, necrotic deposits and staining reproduced in a no-primary control as reasons to investigate artefact (HPA subcellular; standard IHC practice). Check peroxidase blocking and DAB development when pigment or diffuse deposits obscure cell boundaries (standard IHC practice). Interpret the selected carcinoma image as evidence of staining under its stated retrieval and detection conditions, not proof that every positive cell is CR1-specific (datasheet A01022-1; HPA tissue IHC).
Boster reagents
Best CR1 / Complement receptor type 1 IHC Antibodies
The IHC-validated antibody has image evidence from paraffin sections of human endometrial carcinoma, oesophagus squama cancer, and tonsil (A01022-1 image captions). No IF image is supplied (catalog payload).
Real IHC data
Anti-CD35/CR1 Antibody ®
Cat # A01022-1
A01022-1 is the only SKU with a rendered card; its IHC captions show staining in paraffin sections of human endometrial carcinoma, oesophagus squama cancer, and tonsil (A01022-1 image captions). Its listed applications include IHC, and its listed reactivity is human (catalog: A01022-1).
Which to pick: For tissue IHC, choose A01022-1 because its own images document staining in human paraffin sections; the fixative is unreported (A01022-1 image captions). For IF/ICC, M01022-2 is listed for both applications, but no IF image is supplied (catalog: M01022-2). None of the listed SKUs has documented cross-species reactivity; all list human only (catalog: A01022-1, M01022-2, M01022-3).
Each figure is that product's own IHC / IF validation image from its datasheet.
References
- UniProt Consortium. UniProt entry P17927 (CR1_HUMAN, Complement receptor type 1).
- Human Protein Atlas. CR1 tissue IHC expression (reliability: Enhanced).
- Human Protein Atlas. CR1 subcellular location (ICC-IF): Localized to the plasma membrane..
- Human Protein Atlas. CR1 antibody validation summary (5 antibodies).
- Peripheral complement interactions with amyloid β peptide in Alzheimer's disease: Polymorphisms, structure, and function of complement receptor 1. Alzheimer's & dementia : the journal of the Alzheimer's Association 2018 — PMC6231989.
- Optimal germinal center B cell activation and T-dependent antibody responses require expression of the mouse complement receptor Cr1. Journal of immunology (Baltimore, Md. : 1950) 2013 — PMC3707406.
- Complement receptor 1 is expressed on brain cells and in the human brain. Glia 2023 — PMC10953339.
- Dynamic regulation of the cancer stem cell compartment by Cripto-1 in colorectal cancer. Cell death and differentiation 2015 — PMC4563784.
- PubMed PMID:2972794 — UniProt-cited evidence.
- PubMed PMID:8245463 — UniProt-cited evidence.
- PubMed PMID:16710414 — UniProt-cited evidence.
Immunohistochemistry protocol sheet for CR1 (Complement receptor type 1). Expected localisation Membrane expected; tissue subcellular pattern unreported (UniProt; HPA tissue IHC). Antigen retrieval: EDTA pH 8.0 HIER, heat-mediated (datasheet A01022-1). Validated IHC antibody: A01022-1 at 2-5μg/ml (the product's own IHC validation image is shown). Controls (HPA): positive Appendix (Lymphoid tissue); negative Adipose tissue. IHC-P workflow on paraffin sections; fixative unspecified. Protocol steps: 1. Sample: Paraffin-embedded human endometrial carcinoma tissue; fixative not specified (datasheet A01022-1); 2. Fixation: Image fixative and duration unreported (datasheet A01022-1); 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: EDTA pH 8.0 (datasheet A01022-1); 20 min, 95–100 °C (standard); 6. Peroxidase block: 3% H2O2, 10 min , room temperature (standard); 7. Blocking: 10% goat serum (datasheet A01022-1); 8. Primary antibody: Rabbit anti-CR1, 2-5μg/ml (datasheet A01022-1); 9. Primary incubation: Overnight at 4 °C (datasheet A01022-1). Watch for: Fixation: Keep paraffin-section fixation consistent across specimens. (selected-SKU IHC image A01022-1); Caveat: Antibody staining may reflect products of multiple genes (HPA tissue IHC); Isoform / epitope: No isoforms listed; extracellular versus cytoplasmic epitope matters (UniProt); Regulation: No tissue-staining regulator reported (UniProt; HPA tissue IHC). Evidence: UniProt P17927, HPA tissue IHC · Enhanced, HPA ICC-IF · plasma membrane., Datasheet A01022-1, PMC6231989, PMC3707406. QR code links to https://www.bosterbio.com/bosterbio-gene-info-cards/CR1/immunohistochemistry-ihc-guide.