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C5AR1 / C5a anaphylatoxin chemotactic receptor 1 · IHC design guide
Design Immunohistochemistry for C5AR1
Plan chromogenic IHC for C5AR1 using high-staining bone marrow hematopoietic cells or spleen red pulp cells as reference tissues (HPA tissue IHC). This guide covers expected staining, antibody selection and interpretation for paraffin sections.
Evidence assembled Oct 2026 · For research use; verify linked source records and product datasheet before use
C5AR1 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 | Membranous and cytoplasmic staining in immune-cell subsets (HPA tissue IHC) | |
| Staining pattern | Subset immune cells show membranous and cytoplasmic staining (HPA tissue IHC) | |
| Antigen retrieval | EDTA pH 8.0 HIER, heat-mediated (datasheet A01898-3) | |
| Positive control | Bone marrow+4 more · see all | |
| Negative control | Breast+4 more · see all |
Important caveats
Reasons your staining may differ from the expected pattern.
| Fixation | Keep paraffin-section fixation consistent across samples. (standard IHC practice; not target-specific) | |
| Caveat | Phosphorylated receptor can internalize into vesicles (UniProt) | |
| Regulation | Phosphorylation-linked internalization (UniProt) | |
| Isoform / epitope | No annotated isoforms; extracellular versus cytoplasmic epitopes matter (UniProt) |
Section 1
Recommended C5AR1 IHC & IF Protocols
The catalog antibody protocol uses heat-mediated EDTA retrieval at pH 8.0 (datasheet: A01898-3). One published mouse paw IHC protocol is included (PMC12202429).
| Sample | Paraffin-embedded human spleen tissue; fixative not specified (datasheet A01898-3) |
| Fixation | Image fixative and duration unreported (datasheet A01898-3); 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 A01898-3); 20 min, 95–100 °C (standard) |
| Peroxidase block | 3% H2O2, 10 min, room temperature (standard) |
| Blocking | 10% goat serum (datasheet A01898-3) |
| Primary antibody | Rabbit anti-C5AR1, 1:50 recommended; image 1:200 (datasheet A01898-3) |
| Primary incubation | Overnight at 4 °C (datasheet A01898-3) |
| Detection | HRP-conjugated secondary, DAB chromogen (datasheet A01898-3) |
| Counterstain | Hematoxylin, blue, dehydrate and mount (standard) |
| Expected result | C5AR1-positive staining in hematopoietic cells of bone marrow (HPA tissue IHC: High). HPA tissue profile: Cytoplasmic and membranous expression in subsets of immune cells in several tissues. No signal in the no-primary control. |
💡Decision noteStart with EDTA pH 8.0 for the catalog antibody (datasheet: A01898-3). The published mouse paw protocol used citrate pH 6.0 with a different antibody (PMC12202429).
Section 2
What Is the Expected C5AR1 Staining Pattern?
C5AR1 is a seven-transmembrane receptor at the cell membrane and in cytoplasmic vesicles (UniProt P21730 topology and subcellular location). In paraffin-section IHC, expect cytoplasmic and membranous staining in subsets of immune cells across several tissues (HPA tissue IHC). HPA rates this tissue pattern Approved, with medium consistency between staining and RNA expression; interpret individual stained cells in their tissue context (HPA tissue IHC).
| Membranous staining with cytoplasmic signal in selected immune cells, including lung macrophages. | This fits the reported tissue pattern and receptor locations (HPA: medium in lung macrophages; UniProt P21730: cell membrane and cytoplasmic vesicles). Score the relevant cells and compartments, since HPA describes staining in subsets rather than every cell in a section (HPA tissue IHC). |
| Predominantly nuclear staining, without a credible membranous or cytoplasmic pattern. | Nuclear localisation is outside the supplied C5AR1 locations (UniProt P21730 subcellular location; HPA tissue IHC). Treat it as suspect staining; review the negative control and detection steps before assigning it to C5AR1 (general IHC practice). |
| Strong staining in a cell population reported as not detected, such as breast adipocytes. | This conflicts with the reported cell-specific result (HPA: breast adipocytes not detected). Cross-reactivity or endogenous detection activity is possible; check a negative control and whether the signal follows the expected cellular pattern (general IHC practice). |
| Diffuse colour over tissue and empty areas, obscuring cell borders. | A field-wide haze cannot establish the selected-cell membranous and cytoplasmic pattern (HPA tissue IHC). Consider excess antibody or detection background, and compare with a negative control processed alongside the section (general IHC practice). |
| No convincing signal in hematopoietic cells of bone marrow or cells in splenic red pulp. | Those populations are reported High and provide useful comparison material (HPA: bone marrow hematopoietic cells High; spleen red-pulp cells High). Confirm that the relevant cells are present, then assess the control and staining run before interpreting a negative specimen (general IHC practice). |
💡Expected C5AR1 appearanceA convincing positive is High cytoplasmic and membranous staining in the specified bone-marrow hematopoietic cells or splenic red-pulp cells (HPA tissue IHC); isolated nuclear colour or uniform field-wide staining is suspect against the reported localisation (HPA tissue IHC; UniProt P21730 subcellular location).
| Cell population and tissue | HPA reports High staining in bone-marrow hematopoietic cells and splenic red-pulp cells, Medium in lung macrophages, and no detection in breast adipocytes (HPA tissue IHC). Compare the same cell population when judging intensity; an unrelated cell in a positive tissue is not an equivalent control (general IHC practice). |
| Receptor location and trafficking | Seven transmembrane segments support a membrane-associated pattern (UniProt P21730 topology). Cytoplasmic vesicular signal can also fit C5AR1: phosphorylated receptor colocalizes with ARRB1 and ARRB2 in vesicles, and their interaction is associated with internalisation (UniProt P21730 subcellular location and subunit). |
| Evidence strength | The tissue pattern is Approved but has medium consistency with RNA expression, so use it as an expected pattern rather than a guarantee for every specimen (HPA tissue IHC). HPA lists IHC Approved for HPA014520 and CAB002720; those statuses do not establish the performance of another antibody (HPA antibodies). |
| Epitope position | C5AR1 has extracellular, transmembrane and cytoplasmic regions (UniProt P21730 topology). An antibody's epitope position would affect which region its staining assesses, but no epitope position is supplied here; do not infer a required retrieval method from topology alone (UniProt P21730 topology; general IHC practice). |
| IF/ICC Q: Should Golgi staining match paraffin-section IHC? | A: HPA reports mainly Golgi and additional vesicular localisation in ICC-IF, whereas its tissue IHC profile is cytoplasmic and membranous in immune-cell subsets (HPA subcellular ICC-IF; HPA tissue IHC). Compare each result with its own preparation and cell context; the ICC-IF finding does not establish a paraffin IHC pattern. |
| Situation | Likely cause | Next action |
|---|---|---|
| Expected positive cells show no stain. | The relevant cells may be absent from the section, or the staining run may have failed; HPA reports High signal specifically in bone-marrow hematopoietic cells and splenic red-pulp cells (HPA tissue IHC). | Verify those cells on the section and assess a concurrently stained known-positive section and detection controls before calling the sample negative (general IHC practice). |
| The whole section has weak or diffuse colour. | General detection background or excessive primary-antibody signal may obscure the selected-cell pattern (general IHC practice; HPA tissue IHC pattern). | Compare with a primary-antibody omission control, review blocking and washes, and optimise primary-antibody dilution using the antibody's IHC instructions (general IHC practice). |
| Nuclei dominate the signal. | That compartment does not match the supplied cell-membrane or cytoplasmic-vesicle locations (UniProt P21730 subcellular location). Nonspecific binding or detection artefact is possible (general IHC practice). | Check the omission control and whether any membranous or cytoplasmic signal remains in HPA-reported positive cells; withhold a C5AR1 call if it does not (HPA tissue IHC; general IHC practice). |
| A reportedly negative cell type stains strongly. | For example, HPA reports no detection in breast adipocytes; apparent signal there may reflect cross-reactivity or endogenous detection activity (HPA tissue IHC; general IHC practice). | Check the same cell type in an appropriate control section and inspect the omission control. Address endogenous detection activity as appropriate to the chromogenic system (general IHC practice). |
| Only cytoplasmic puncta are visible. | Vesicular C5AR1 is plausible, including receptor associated with ARRB1 and ARRB2 after phosphorylation (UniProt P21730 subcellular location and subunit). Puncta alone do not establish antibody specificity (general IHC practice). | Assess whether puncta occur in the expected cells, compare the negative control, and review any membranous component against the HPA tissue profile (HPA tissue IHC; general IHC practice). |
| A medium- or low-staining tissue appears negative. | HPA levels vary by tissue and cell: lung macrophages are Medium, stomach glandular cells Low, and several listed cell populations are not detected (HPA tissue IHC). | Check the specified cell population and a High reference population before treating the finding as a staining failure; report the examined cells and control result (HPA tissue IHC; general IHC practice). |
Experiment evidence
IHC & IF images showing C5AR1 staining
A01898-3 · IHCIHC analysis of C5AR1 using anti-C5AR1 antibody (A01898-3). C5AR1 was detected in a paraffin-embedded section of human spleen tissue. Heat m
A01898S334 · IHCImmunohistochemistry (IHC) analyzes of C5aR (S334) pAb in paraffin-embedded human breast carcinoma tissue at 1:100.
A01898S338 · IHCImmunohistochemistry analysis of paraffin-embedded human brain, using CD88/C5aR (Phospho-Ser338) Antibody. The picture on the right is block
HPA · Cerebral cortexHuman Protein Atlas IHC, Cerebral cortex. Source: https://www.proteinatlas.org/ENSG00000197405-C5AR1/tissue/cerebral+cortex#imid_3748560
HPA · ColonHuman Protein Atlas IHC, Colon. Source: https://www.proteinatlas.org/ENSG00000197405-C5AR1/tissue/colon#imid_3748494
HPA · LiverHuman Protein Atlas IHC, Liver. Source: https://www.proteinatlas.org/ENSG00000197405-C5AR1/tissue/liver#imid_3748495
HPA · KidneyHuman Protein Atlas IHC, Kidney. Source: https://www.proteinatlas.org/ENSG00000197405-C5AR1/tissue/kidney#imid_3748496
HPA · ICC-IF A-549Human Protein Atlas immunofluorescence, A-549, antibody HPA048012; green = C5AR1, blue = nucleus, red = microtubules.
HPA · ICC-IF A-549Human Protein Atlas immunofluorescence, A-549, antibody HPA048012; green = C5AR1, blue = nucleus, red = microtubules.
← swipe / scroll for more images →
Real IHC / IF data behind the staining-pattern expectations in this section.
Sample controls for C5AR1 IHC & IF
🧪Run spleen first: cells in the red pulp should stain (HPA: High in spleen red pulp; catalog antibody A01898-3: spleen paraffin-section IHC). Use breast adipocytes as the negative tissue (HPA: Not detected in breast adipocytes); on the spleen slide, assess morphologically distinct cells without specific staining as internal background comparators, without assuming every cell outside the red pulp is negative.
Positive control tissue: Bone marrow (Hematopoietic cells, HPA High)
Negative control tissue: Breast (HPA Not detected)
ICC-IF cell lines (HPA subcellular resource): HPA ICC-IF images show C5AR1 in A-549, HeLa, U2OS, with annotated localisation: Golgi apparatus (approved) (HPA subcellular).
Technical controls: Include a no-primary, secondary-only control and a rabbit IgG control matched to the primary antibody’s isotype and clonality where applicable (catalog antibody A01898-3 caption: rabbit primary and peroxidase-conjugated goat anti-rabbit secondary); use C5AR1 knockout material processed in parallel as a biological negative when available. Quench endogenous peroxidase and distinguish red-pulp blood pigment from DAB staining (catalog antibody A01898-3 caption: spleen red-pulp IHC with HRP/DAB).
⚠️Feasibility: The spleen paraffin-section example uses heat retrieval in EDTA at pH 8.0 and a primary dilution of 1:200, but it does not establish that retrieval is required under every condition (catalog antibody A01898-3 caption). A target-specific fixation window or fixation effect is unreported, and the selected caption does not state the fixative (catalog antibody A01898-3 caption). Frozen sections are not established as easier; ICC-IF images exist for A-549, HeLa and U2OS, with mainly Golgi and additional vesicle localization (HPA: C5AR1 subcellular), while spleen red-pulp blood pigment can complicate chromogenic interpretation (catalog antibody A01898-3 caption: spleen HRP/DAB IHC).
HPA tissue IHC evidence for C5AR1
Comprehensive Human Protein Atlas IHC scoring per tissue (reliability: Approved — Medium consistency between antibody staining and RNA expression data.). Rows are taken directly from the HPA tissue chart — click any row's HPA link to view the source.
Positive expression · recommended positive controls
| Tissue | Cell type | Level | Evidence | Source |
|---|---|---|---|---|
| Bone marrow | Hematopoietic cells | High | Protein (IHC) | HPA → |
| Spleen | Cells in red pulp | High | Protein (IHC) | HPA → |
| Adrenal gland | Glandular cells | Medium | Protein (IHC) | HPA → |
| Appendix | Lymphoid tissue | Medium | Protein (IHC) | HPA → |
| Cerebral cortex | Neuropil | Medium | Protein (IHC) | HPA → |
Undetected expression · recommended negative controls
| Tissue | Cell type | Level | Evidence | Source |
|---|---|---|---|---|
| Breast | Adipocytes | Not detected | Protein (IHC) | HPA → |
| Bronchus | Basal cells | Not detected | Protein (IHC) | HPA → |
| Cerebellum | Cells in granular layer | Not detected | Protein (IHC) | HPA → |
| Cervix | Glandular cells | Not detected | Protein (IHC) | HPA → |
| Duodenum | Glandular cells | Not detected | Protein (IHC) | HPA → |
Section 3
Advanced C5AR1 IHC Tips
Troubleshoot C5AR1 staining in paraffin sections by checking retrieval, cell identity, subcellular pattern, and controls before interpreting signal.
What retrieval should I try first when C5AR1 staining is weak?
Start with heat-mediated antigen retrieval in EDTA at pH 8.0 for the catalog antibody (datasheet A01898-3). The documented paraffin-section workflow used 1:200 primary antibody overnight at 4°C after that retrieval, so reproduce those conditions before changing several variables together (datasheet A01898-3). If staining remains weak, vary heating time on adjacent sections while holding the antibody concentration, detection chemistry, and tissue processing constant (standard IHC practice). Compare signal in spleen red-pulp cells with background in neighboring structures, because strong staining of red-pulp cells is reported while C5AR1 expression is restricted to subsets of immune cells across tissues (HPA tissue IHC).
Could fixation explain inconsistent C5AR1 staining between paraffin blocks?
Target-specific sensitivity to fixation is unknown: the selected antibody caption describes a paraffin-embedded spleen section but does not state its fixative (datasheet A01898-3). Record each block’s fixative, fixation duration, and processing history, then compare sections under the same EDTA pH 8.0 retrieval and 1:200 primary-antibody conditions used in the documented workflow (datasheet A01898-3; standard IHC practice). Include a similarly processed positive-control section in each staining run to distinguish a block-dependent loss of signal from a failed run (standard IHC practice). Do not attribute a difference specifically to altered C5AR1 epitopes without matched fixation comparisons, because the supplied evidence contains no such comparison (datasheet A01898-3).
Should I expect C5AR1 at the membrane or inside cells?
Assess both membranous and cytoplasmic staining in the relevant cells: C5AR1 is annotated at the cell membrane and in cytoplasmic vesicles, and HPA reports cytoplasmic and membranous expression in immune-cell subsets (UniProt P21730 subcellular location; HPA tissue IHC). Vesicular signal can be biologically plausible because phosphorylated C5AR1 colocalizes with ARRB1 and ARRB2 during receptor internalization (UniProt P21730 subcellular location and subunit). In paraffin sections, first identify positive cells by morphology and tissue compartment, then score membrane and cytoplasmic signal separately (standard IHC practice). Diffuse staining throughout an unrelated cell population needs control-based confirmation, even when its intensity resembles the expected signal (HPA tissue IHC; standard IHC practice).
How should epitope uncertainty affect my C5AR1 staining strategy?
Do not assume which side of C5AR1 the catalog antibody recognizes unless its immunogen or mapped epitope is documented; none is specified in the supplied antibody caption (datasheet A01898-3). The receptor has 7 transmembrane segments, an extracellular N terminus spanning residues 1–37, and a cytoplasmic C terminus spanning 304–350 (UniProt P21730 topology). Its annotated modifications include glycosylation at residue 5, sulfation at 11 and 14, and C-terminal phosphorylation sites, so epitope accessibility may depend on the region recognized (UniProt P21730 modifications; standard IHC practice). UniProt lists 0 annotated isoforms; interpret staining as receptor localization rather than assigning an unsupported isoform (UniProt P21730 isoforms).
How can I check C5AR1 localization by IF alongside tissue IHC?
Treat IF as a separate assay and multiplex C5AR1 with a marker for the expected immune-cell population, particularly where tissue IHC shows staining in subsets of immune cells (HPA tissue IHC; standard IF practice). Choose a fluorophore channel with low measured tissue autofluorescence, and use single-stain controls to assess bleed-through before interpreting overlap (standard IF practice). Set permeabilisation according to the antibody’s mapped epitope: intracellular epitopes require access through the membrane, whereas excessive permeabilisation can compromise assessment of an accessible extracellular epitope (UniProt P21730 topology; standard IF practice). HPA reports Golgi and vesicular IF localization, while UniProt also annotates cell-membrane and cytoplasmic-vesicle localization; compare compartments without requiring exact agreement across assays (HPA subcellular; UniProt P21730 subcellular location).
How do I distinguish C5AR1 signal from chromogenic background?
Run a no-primary control and inspect it alongside the stained section to identify signal from detection reagents or endogenous tissue activity (standard IHC practice). Include an endogenous peroxidase block before HRP/DAB detection, and keep development time consistent across sections when comparing intensity (standard IHC practice). The documented spleen workflow used 10% goat serum blocking, 1:200 primary antibody overnight at 4°C, and an HRP/DAB readout; use those details as the antibody-specific starting point (datasheet A01898-3). If background persists, adjust blocking, washes, primary concentration, or DAB development one variable at a time, while checking whether spleen red-pulp cells remain identifiable as expected positives (HPA tissue IHC; standard IHC practice).
What should I count when comparing C5AR1 staining across sections? ⚠ ANSWER MARKED FOR VERIFICATION
Define the cell population and tissue compartment before scoring, because HPA reports C5AR1 in subsets of immune cells rather than uniformly across a section (HPA tissue IHC). For a specified population, record the percentage of positive cells and staining intensity, or calculate an H-score from intensity categories 0–3 and their percentages, yielding 0–300 (standard IHC practice). When spatial infiltration matters, report positive-cell density per mm² of viable tissue and separate membrane from cytoplasmic staining if both are present (standard IHC practice; UniProt P21730 subcellular location). Normalize counts to the eligible cell population or viable area, using the same threshold, sampling scheme, and control tissue across sections (standard IHC practice).
When is apparent C5AR1 positivity likely to be an artefact?
Give greatest weight to staining in plausible cells and compartments: HPA reports high signal in spleen red-pulp cells and bone-marrow hematopoietic cells, while UniProt places C5AR1 at membranes and in cytoplasmic vesicles (HPA tissue IHC; UniProt P21730 subcellular location). Signal confined to section edges, necrotic areas, or the no-primary control should prompt review of processing and detection background before biological interpretation (standard IHC practice). Check for residual endogenous peroxidase activity when DAB appears broadly in tissue unrelated to the expected cell distribution (standard IHC practice; HPA tissue IHC). Even convincing morphology is insufficient alone for a new cell-type claim; verify the pattern with appropriate controls and independent evidence (standard IHC practice).
Boster reagents
Best C5AR1 / C5a anaphylatoxin chemotactic receptor 1 IHC Antibodies
Anti-C5AR1 antibodies have IHC images from paraffin-embedded human spleen, breast carcinoma and brain (catalog image captions); all three list IF, and two list mouse and rat reactivity (catalog applications/reactivity).
Real IHC data
Anti-C5aR Antibody
Cat # A01898-3
Real IHC data
Anti-C5aR (S334) C5AR1 Antibody
Cat # A01898S334
Real IHC data
Anti-Phospho-CD88 (S338) C5AR1 Antibody
Cat # A01898S338
A01898-3 shows IHC in human spleen paraffin sections, and A01898S334 shows IHC in human breast carcinoma paraffin sections (respective image captions). A01898S338 shows phospho-Ser338 IHC in human brain paraffin sections with a phosphopeptide blocking comparison (A01898S338 image caption).
Which to pick: For tissue IHC, A01898-3 has a human spleen paraffin example using EDTA retrieval and 1:200 primary antibody; its listed IHC dilution is 1:50 (A01898-3 image caption; catalog dilution). For IF/ICC, choose A01898-3 because this polyclonal antibody lists both applications and human reactivity; for human, mouse or rat IHC/IF, consider A01898S334 or the phospho-Ser338 antibody A01898S338, whose IHC images are from human breast carcinoma and human brain, respectively (A01898-3 datasheet/applications/reactivity; A01898S334 and A01898S338 applications/reactivity and image captions). The fixative is unreported in all three paraffin IHC captions (catalog image captions).
Each figure is that product's own IHC / IF validation image from its datasheet.
References
- UniProt Consortium. UniProt entry P21730 (C5AR1_HUMAN, C5a anaphylatoxin chemotactic receptor 1).
- Human Protein Atlas. C5AR1 tissue IHC expression (reliability: Approved).
- Human Protein Atlas. C5AR1 subcellular location (ICC-IF): Mainly localized to the Golgi apparatus. In addition localized to vesicles..
- Human Protein Atlas. C5AR1 antibody validation summary (3 antibodies).
- Immunohistochemical identification of complement peptide C5a receptor 1 (C5aR1) in non-neoplastic and neoplastic human tissues. PloS one 2021 — PMC7894821.
- C5a-C5AR1 axis as a potential trigger of the rupture of intracranial aneurysms. Scientific reports 2024 — PMC10850553.
- AduCPI2 alleviates MSU-induced acute gouty arthritis in mice by inhibiting cathepsin S and the C5a-C5aR1 axis. Frontiers in pharmacology 2025 — PMC12202429.
- C5aR1 Promotes Invasion, Metastasis, and Poor Prognosis in Cutaneous Squamous Cell Carcinoma. The American journal of pathology 2025 — PMC12163391.
- PubMed PMID:2007135 — UniProt-cited evidence.
- PubMed PMID:1847994 — UniProt-cited evidence.
- PubMed PMID:15057824 — UniProt-cited evidence.
Immunohistochemistry protocol sheet for C5AR1 (C5a anaphylatoxin chemotactic receptor 1). Expected localisation Membranous and cytoplasmic staining in immune-cell subsets (HPA tissue IHC). Antigen retrieval: EDTA pH 8.0 HIER, heat-mediated (datasheet A01898-3). Validated IHC antibody: A01898-3 at 1:50 recommended; image 1:200 (the product's own IHC validation image is shown). Controls (HPA): positive Bone marrow (Hematopoietic cells); negative Breast. IHC-P workflow on paraffin sections; fixative unspecified. Protocol steps: 1. Sample: Paraffin-embedded human spleen tissue; fixative not specified (datasheet A01898-3); 2. Fixation: Image fixative and duration unreported (datasheet A01898-3); 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 A01898-3); 20 min, 95–100 °C (standard); 6. Peroxidase block: 3% H2O2, 10 min , room temperature (standard); 7. Blocking: 10% goat serum (datasheet A01898-3); 8. Primary antibody: Rabbit anti-C5AR1, 1:50 recommended; image 1:200 (datasheet A01898-3); 9. Primary incubation: Overnight at 4 °C (datasheet A01898-3). Watch for: Fixation: Keep paraffin-section fixation consistent across samples. (standard IHC practice; not target-specific); Caveat: Phosphorylated receptor can internalize into vesicles (UniProt); Isoform / epitope: No annotated isoforms; extracellular versus cytoplasmic epitopes matter (UniProt); Regulation: Phosphorylation-linked internalization (UniProt). Evidence: UniProt P21730, HPA tissue IHC · Approved, HPA ICC-IF · Mainly localized to the Golgi apparatus. In addition localized to…, Datasheet A01898-3, PMC12202429. QR code links to https://www.bosterbio.com/bosterbio-gene-info-cards/C5AR1/immunohistochemistry-ihc-guide.