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CR1 / Complement receptor type 1 · IHC design guide
Design Immunohistochemistry for CR1
Plan CR1 chromogenic IHC on paraffin sections with the catalog antibody at 2–5 µg/mL (datasheet A01022-1). Use tonsil germinal-center staining as a reference (HPA tissue IHC), assess the membrane expectation (UniProt), and consider the HPA antibody-specificity caution (HPA tissue IHC).
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 (UniProt); glomerular and immune cells stain (HPA tissue IHC) | |
| Staining pattern | Medium staining in glomerular and germinal-center cells (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 | Matched tissue-IHC evidence does not establish the fixation claim. Validate the specimen-specific method before use. (selected-SKU IHC image A01022-1) | |
| Caveat | HPA antibody may detect proteins from multiple genes (HPA tissue IHC) | |
| Regulation | Regulation unspecified in the supplied record (UniProt) | |
| Isoform / epitope | No isoforms listed; extracellular versus cytoplasmic epitope matters (UniProt) |
Section 1
Recommended CR1 IHC & IF Protocols
The catalog antibody protocol uses FFPE sections (datasheet A01022-1); the published options cover neocortex (PMC6231989) and mouse spleen (PMC3707406).
| 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 noteStart with heat-mediated EDTA retrieval at pH 8.0 for the catalog antibody (datasheet A01022-1). The published frozen-section protocols do not specify retrieval (PMC6231989; PMC3707406).
Section 2
What Is the Expected CR1 Staining Pattern?
CR1 is a cell-surface receptor with an extracellular region spanning residues 42–1971 and one transmembrane segment (UniProt P17927 topology). In paraffin-section IHC, expect selective staining in renal glomeruli and in subsets of immune cells and follicular dendritic cells in lymphoid tissue (HPA tissue IHC). HPA rates the tissue pattern Enhanced, while reporting medium antibody–RNA consistency and cautioning that the antibodies may detect protein from more than one gene (HPA tissue IHC).
| Selective staining outlines cells in glomeruli or appears among germinal-center and white-pulp cells (HPA tissue IHC). | This fits the reported CR1 distribution; glomerular cell identity is unspecified, and the listed positive compartments have Medium HPA staining (HPA tissue IHC). Assess the cellular pattern alongside a negative control (general IHC practice). |
| Strong, predominantly nuclear staining or uniform staining throughout the cytoplasm appears (general IHC practice). | That compartment conflicts with the membrane location supported by UniProt and HPA ICC-IF (UniProt P17927 topology; HPA subcellular). Treat it as suspect until a control and an independently validated antibody support the pattern (general IHC practice; HPA antibody validation). |
| Adipocytes or respiratory epithelial cells stain prominently (general IHC practice). | HPA reports those cell types as Not detected (HPA tissue IHC). Investigate antibody cross-reactivity and endogenous chromogen activity before assigning CR1 positivity; an HPA negative is a comparator, not proof that every specimen must be negative (general IHC practice; HPA tissue IHC). |
| Color spreads across tissue without clear cellular boundaries (general IHC practice). | This does not reproduce the highly selective HPA pattern (HPA tissue IHC). Assess nonspecific binding, excess detection signal and incomplete washing with controls (general IHC practice); diffuse color alone cannot establish CR1 expression. |
| No staining appears in glomeruli or a germinal center selected as a positive reference (HPA tissue IHC). | An absent reference signal makes a negative test specimen difficult to interpret (general IHC practice). Check assay controls and antibody performance first; HPA reports Medium, rather than universal, staining in these compartments (HPA tissue IHC). |
💡Expected CR1 appearanceCall a result consistent with CR1 when selective, mainly cell-surface staining occurs in HPA-reported glomerular or lymphoid cell populations at an interpretable Medium reference level; prominent nuclear, diffuse or HPA-discordant cell-type staining is suspect (HPA tissue IHC; UniProt P17927 topology; general IHC practice).
| Membrane topology and epitope location | CR1 has an extracellular region at residues 42–1971, a transmembrane segment at 1972–1996 and a cytoplasmic region at 1997–2039 (UniProt P17927 topology). Interpret cellular localisation against that topology; the supplied record does not identify the catalog antibody's epitope. |
| Tissue reference and antibody validation | HPA reports Medium staining in glomeruli, germinal centers, white pulp and bone-marrow hematopoietic cells (HPA tissue IHC). Several listed antibodies have Enhanced IHC validation, yet HPA also flags medium antibody–RNA consistency and possible detection of protein from more than one gene (HPA antibody validation; HPA tissue IHC). |
| Glycosylation and processing | UniProt lists 20 glycosylation sites, a signal peptide at residues 1–41 and a mature chain beginning at residue 42 (UniProt P17927). Without an antibody epitope or target-specific IHC evidence, these annotations do not predict staining intensity or an antigen-retrieval condition. |
| Paraffin-section workflow | Antigen retrieval, blocking, detection controls and counterstaining are general IHC variables (general IHC practice). Their CR1-specific effects are unreported here; neither HPA staining levels nor UniProt topology establish a fixation effect (HPA tissue IHC; UniProt P17927 topology). |
| IF/ICC Q: Where should CR1 appear? | A: HPA supports plasma-membrane localisation in ICC-IF and lists HEL among lines with images (HPA subcellular). This cross-check supports compartment interpretation; the present section provides no IF/ICC protocol option. |
| Situation | Likely cause | Next action |
|---|---|---|
| An HPA-reported positive reference is blank (HPA tissue IHC). | Assay failure or insufficient detection is possible (general IHC practice); absence in one field alone does not overturn HPA's Medium compartment-level report (HPA tissue IHC). | Confirm the reference compartment, inspect positive and negative controls, and review the catalog antibody's IHC-P conditions (general IHC practice). |
| Glomerular staining is absent, but lymphoid staining is present (HPA tissue IHC). | HPA reports both as positive compartments without asserting identical staining in every section (HPA tissue IHC). Tissue sampling or assay variation may contribute (general IHC practice). | Score each compartment separately, inspect morphology and controls, and avoid calling the entire run negative from one compartment (general IHC practice). |
| Nuclei dominate the signal (general IHC practice). | Predominantly nuclear color conflicts with the supported plasma-membrane location (UniProt P17927 topology; HPA subcellular). Its specific source cannot be inferred from appearance alone. | Check the no-primary control and staining distribution, then seek concordance with an independently validated IHC antibody (general IHC practice; HPA antibody validation). |
| Adipocytes or respiratory epithelium show conspicuous color (general IHC practice). | Those cells are reported as Not detected by HPA; cross-reactivity or endogenous chromogenic activity is possible (HPA tissue IHC; general IHC practice). | Compare a no-primary control, review endogenous-activity blocking, and confirm any unexpected cellular pattern independently (general IHC practice). |
| Diffuse color obscures cell borders (general IHC practice). | Nonspecific binding, detection background or inadequate washing may obscure the selective pattern reported by HPA (general IHC practice; HPA tissue IHC). | Review blocking, washing, detection and counterstain conditions against run controls; score CR1 only where cellular localisation remains interpretable (general IHC practice). |
| Two antibodies give different tissue patterns (general IHC practice). | HPA's Enhanced IHC assessments coexist with a caution about detection of protein from more than one gene (HPA antibody validation; HPA tissue IHC). Discordance alone does not identify which pattern is specific. | Compare each result with HPA positive and negative cell types, membrane localisation and assay controls before assigning CR1 expression (HPA tissue IHC; UniProt P17927 topology; general IHC practice). |
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 look for staining in germinal center cells (HPA: Medium in lymph-node germinal center cells). Use adipose tissue as the negative tissue (HPA: Not detected in adipocytes); on the lymph-node slide, treat morphologically identified unstained cells outside the germinal centers as internal negatives, without assuming every lymphocyte lacks CR1 (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 an isotype control matched to the primary antibody’s host species and clonality; the caption identifies rabbit IgG but does not state clonality (selected-SKU caption: rabbit anti-CD35 antibody). A CR1 knockout specimen, if available, provides a biological negative; quench endogenous peroxidase and inspect background in the lymphoid tissue before interpreting DAB staining (standard chromogenic IHC practice).
⚠️Feasibility: A target-specific fixation window or fixation effect is unreported, and the selected-SKU paraffin-section caption does not report a fixative (selected-SKU caption: fixative not stated). The caption uses heat retrieval in EDTA at pH 8.0, but does not establish whether retrieval is required or optimal (selected-SKU caption: EDTA heat retrieval). For IF/ICC, plasma-membrane localization is supported in HEL images (HPA subcellular: plasma membrane); the supplied evidence does not establish that frozen sections or IF are easier, and endogenous peroxidase in lymphoid cells can complicate chromogenic interpretation (standard IHC practice).
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
Use cell-specific controls and membrane localisation to troubleshoot CR1 staining in paraffin sections; the catalog image establishes one retrieval and detection workflow.
What retrieval should I try first when CR1 staining is weak in paraffin sections?
Start with heat-mediated retrieval in EDTA at pH 8.0 (datasheet A01022-1). The catalog image used that retrieval for a paraffin section, followed by 2 μg/ml primary antibody overnight at 4°C and DAB detection (datasheet A01022-1). If staining remains weak, adjust heating time in small steps while processing a known positive section alongside the test section (standard IHC practice; HPA: CR1 staining in renal glomeruli and lymphoid germinal centers). Compare membrane staining and tissue preservation at each setting, because stronger overall color alone does not establish specific CR1 detection (UniProt P17927 topology; standard IHC practice).
How should I assess whether fixation caused weak CR1 staining?
The catalog caption identifies a paraffin section but does not report its fixative, so target-specific CR1 fixation sensitivity is unknown (datasheet A01022-1). Record the fixative, fixation duration, specimen thickness and processing history for each section, then compare sections handled under documented conditions using the same retrieval and detection run (standard IHC practice). Check whether expected membrane staining appears in an internal positive population before attributing a weak result to fixation (UniProt P17927 topology; UniProt P17927 tissue specificity). Include a no-primary control to separate nonspecific detection from lost antigen signal, and avoid treating HPA tissue patterns as evidence for a particular fixation condition (standard IHC practice; HPA: tissue IHC profile).
Where should convincing CR1 signal appear within a positive cell?
Look for cell-surface staining: CR1 has an extracellular region at residues 42–1971, one transmembrane segment at 1972–1996 and a cytoplasmic tail at 1997–2039 (UniProt P17927 topology). Supported plasma membrane localisation provides an independent expectation for the staining pattern (HPA: subcellular localisation). Assess that pattern in plausible positive populations, including cells in renal glomeruli and lymphoid germinal centers, rather than judging an entire section by its average color (HPA: tissue IHC profile). Diffuse nuclear color or uniform staining across unrelated cells warrants review of counterstain, detection and negative controls before it is scored as CR1 (standard IHC practice; UniProt P17927 topology).
How can epitope location change my interpretation of CR1 staining?
First establish which region the antibody recognizes; the supplied record does not specify the catalog antibody’s epitope (datasheet A01022-1; UniProt P17927 record). CR1 presents 30 extracellular Sushi domains before its transmembrane segment, while its cytoplasmic region spans residues 1997–2039 (UniProt P17927 topology). The record lists 20 glycosylation sites and 0 annotated isoforms, but neither fact identifies the antibody’s binding site or proves that an apparent staining difference reflects an isoform (UniProt P17927 glycosylation and isoform fields). Compare independently verified epitopes and matched positive controls if staining differs between specimens, while keeping retrieval and detection conditions documented (standard IHC practice).
How should I plan a follow-up IF experiment to clarify CR1-positive cells?
For a separate IF experiment, multiplex CR1 with a validated marker for the suspected cell population, then assess whether both signals outline the same cells (UniProt P17927 tissue specificity; standard IF practice). Choose spectrally separated fluorophores after inspecting unstained tissue autofluorescence, and include single-label controls to evaluate bleed-through (standard IF practice). Because CR1 has a large extracellular region and a short cytoplasmic tail, choose permeabilisation according to the antibody’s verified epitope: extracellular labeling may be assessed without permeabilisation, whereas an intracellular-tail epitope requires access across the membrane (UniProt P17927 topology; standard IF practice). The catalog caption documents paraffin-section chromogenic IHC, so establish IF performance independently (datasheet A01022-1).
What should I check when DAB color obscures discrete CR1 staining?
Run a no-primary control through the same secondary antibody and DAB steps to identify background from the detection workflow (standard IHC practice; datasheet A01022-1: DAB detection). Apply a peroxidase block and check blocking and washing conditions before increasing the threshold used to call a section positive (standard chromogenic IHC practice). The catalog image used 10% goat serum blocking, 2 μg/ml primary antibody overnight at 4°C, and secondary incubation for 30 minutes at 37°C (datasheet A01022-1). Evaluate residual color against the expected membrane pattern in selected immune and glomerular cells, since widespread color can conceal that pattern (UniProt P17927 topology; HPA: tissue IHC profile).
How should I quantify CR1 staining across sections with different cell mixtures? ⚠ ANSWER MARKED FOR VERIFICATION
Define the compartment and cell population before scoring, using membrane staining in an annotated region of interest as the CR1 readout (UniProt P17927 topology; standard IHC practice). Report the percentage of positive cells and, when intensity is reproducible, an H-score using the same thresholds across slides (standard IHC practice). For sparse positive cells, report positive-cell density per mm² of evaluable tissue or of the relevant compartment (standard IHC practice). Normalize counts to the number of eligible cells or the measured area, and record excluded necrotic or damaged regions so changes in cell composition do not masquerade as changes in CR1 staining (standard IHC practice).
How can I distinguish true CR1 positivity from a staining artefact?
A credible result combines membrane-associated color with a plausible cell population, such as glomerular cells or lymphoid germinal center cells (UniProt P17927 topology; HPA: tissue IHC profile). Treat dominant nuclear staining, staining confined to section edges or necrotic areas, and color reproduced in the no-primary control as possible artefacts requiring review (standard IHC practice). Check endogenous peroxidase background when DAB color appears broadly, and compare test tissue with a positive control processed in the same run (standard chromogenic IHC practice; datasheet A01022-1: DAB detection). Interpret unexpected widespread staining cautiously because the HPA tissue-IHC reliability note warns that its antibody staining may include protein from more than one gene (HPA: Enhanced reliability description).
Boster reagents
Best CR1 / Complement receptor type 1 IHC Antibodies
A01022-1 has IHC images from human paraffin sections; the supplied catalog contains no IF images (catalog image captions).
Real IHC data
Anti-CD35/CR1 Antibody ®
Cat # A01022-1
A01022-1 lists human IHC reactivity (catalog applications and reactivity). Its images show paraffin sections of human endometrial carcinoma, oesophagus squama cancer, and tonsil; the fixative is unreported (A01022-1 IHC image captions).
Which to pick: Choose A01022-1 for human paraffin-section IHC because it has images using heat retrieval and 2 μg/ml primary antibody (A01022-1 IHC image captions). For IF/ICC, M01022-2 lists those applications at 1:50, but has no supplied IF image; M01022-3 lists IHC without an IHC image (catalog applications, dilutions, and image fields). None of these SKUs has supplied cross-species reactivity: all list Human only (catalog reactivity).
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 (UniProt); glomerular and immune cells stain (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: Matched tissue-IHC evidence does not establish the fixation claim. Validate the specimen-specific method before use. (selected-SKU IHC image A01022-1); Caveat: HPA antibody may detect proteins from multiple genes (HPA tissue IHC); Isoform / epitope: No isoforms listed; extracellular versus cytoplasmic epitope matters (UniProt); Regulation: Regulation unspecified in the supplied record (UniProt). 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.