FCGR2A / Low affinity immunoglobulin gamma Fc region receptor II-a · IHC design guide

Design Immunohistochemistry for FCGR2A

Plan FCGR2A staining in paraffin sections using the observed cytoplasmic pattern in hematopoietic cells and macrophages (HPA tissue IHC). This guide covers fixation consistency and epitope planning for a membrane receptor (UniProt).

Evidence assembled Oct 2026 · For research use; verify linked source records and product datasheet before use

Immunohistochemistry protocol sheet for FCGR2A (IHC for FCGR2A): expected localisation Cytoplasmic in immune cells (HPA tissue IHC); membrane expected (UniProt), antibody A01450-1, validated IHC image, and IHC protocol steps — Printable **FCGR2A** IHC protocol sheet — expected localisation Cytoplasmic in immune cells (HPA tissue IHC); membrane expected (UniProt), antibody A01450-1, controls and protocol steps. Open the full FCGR2A IHC guide →

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FCGR2A 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	Cytoplasmic in immune cells (HPA tissue IHC); membrane expected (UniProt)
	Staining pattern	Cytoplasmic in hematopoietic cells, macrophages and some lymphoid cells (HPA tissue IHC)
	Antigen retrieval	Citrate pH 6 HIER, heat-mediated (datasheet A01450-1)
	Positive control ⓘ	Endometrium+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 fixation consistent across sections (standard IHC practice; not target-specific)
	Caveat	Antibody may stain products of more than one gene (HPA tissue IHC)
	Regulation	Expression varies by cell type (HPA tissue IHC)
	Isoform / epitope	2 isoforms; check extracellular vs cytoplasmic epitope (UniProt)

Section 1

Recommended FCGR2A IHC & IF Protocols

The catalog antibody protocol is accompanied by 3 published FCGR2A IHC protocols for breast carcinoma samples (PMC2987696; PMC2976659; PMC2935495).

Recommended immunohistochemistry (IHC-P) protocol parameters
Sample	Paraffin-embedded human lung cancer tissue; fixative not specified (datasheet A01450-1)
Fixation	Image fixative and duration unreported (datasheet A01450-1); verify before use.
Sectioning	4–5 µm sections on charged slides (standard)
Deparaffinisation	Xylene, graded ethanol series to water (standard)
Antigen retrieval	Heat retrieval: Citrate pH 6, 20 min (datasheet A01450-1)
Peroxidase block	3% H2O2, 10 min, room temperature (standard)
Blocking	10% goat serum (datasheet A01450-1)
Primary antibody	Rabbit anti-FCGR2A, 1μg/ml (datasheet A01450-1)
Primary incubation	Overnight at 4 °C (datasheet A01450-1)
Detection	Streptavidin-biotin complex (SABC), DAB chromogen (datasheet A01450-1)
Counterstain	Hematoxylin, blue, dehydrate and mount (standard)
Expected result	FCGR2A-positive staining in ciliated epithelial cells of endometrium (HPA tissue IHC: High). HPA tissue profile: Cytoplasmic expression in hematopoietic cells, macrophages and subsets of lymphoid cells. No signal in the no-primary control.

💡Decision noteStart with heat-mediated citrate retrieval at pH 6 (datasheet A01450-1); the cited excerpts do not specify retrieval conditions.

Section 2

What Is the Expected FCGR2A Staining Pattern?

FCGR2A is a cell membrane receptor with an extracellular domain and a single transmembrane segment (UniProt P12318 topology). In tissue IHC, expect staining in lung macrophages and bone marrow hematopoietic cells, among other documented populations (HPA: tissue IHC). HPA describes the tissue pattern as cytoplasmic and rates its reliability Supported, with medium agreement between staining and RNA data (HPA: tissue IHC).

What am I looking at on my slide?
Strong staining in lung macrophages, with staining in some other hematopoietic populations.	This fits the observed tissue distribution: lung macrophages are High and bone marrow hematopoietic cells are Medium (HPA: tissue IHC). Score the identified cells separately from surrounding tissue. HPA calls the IHC profile cytoplasmic, while UniProt places FCGR2A at the cell membrane; a chromogenic section may not resolve a narrow membrane rim (HPA: tissue IHC; UniProt P12318 topology).
Predominantly nuclear staining, with little signal in the expected positive cells.	A nuclear-only pattern conflicts with the reported membrane location and the observed cytoplasmic tissue profile (UniProt P12318 topology; HPA: tissue IHC). Treat it as suspect staining. Check the matched negative control and whether a separate detection or counterstain component accounts for the appearance before interpreting it as FCGR2A.
Prominent staining in a cell type expected to be negative.	For example, bronchial respiratory epithelial cells and adipocytes are Not detected in HPA tissue IHC (HPA: bronchus; HPA: adipose tissue). Unexpected signal may reflect antibody cross-reactivity or endogenous detection activity; morphology alone cannot distinguish them. Do not apply a blanket rule that epithelial staining is false: endometrial ciliated epithelial cells are High (HPA: endometrium).
Diffuse color across cells, stroma, and the slide background.	A field-wide haze obscures the cell-restricted pattern reported by HPA (HPA: tissue IHC). In a chromogenic assay, inspect the negative control for nonspecific binding, residual detection activity, or excess chromogen development (general IHC practice). Do not score haze as weak FCGR2A positivity merely because the section contains expected positive cells.
No staining in recognizable lung macrophages or endometrial ciliated epithelial cells.	Those populations are High in HPA tissue IHC, so a blank result raises an assay or specimen question (HPA: lung; HPA: endometrium). First verify that the positive cells are present in the section. Then review the antibody, retrieval, detection reagents, and control run using general IHC practice; the supplied sources do not establish FCGR2A-specific fixation sensitivity.

💡Expected FCGR2A appearanceCall a result positive when identifiable lung macrophages or endometrial ciliated epithelial cells show strong cell-associated staining (HPA: High in both); predominantly nuclear signal or uniform field-wide color is suspect against the reported cytoplasmic IHC profile and membrane topology (HPA: tissue IHC; UniProt P12318 topology).

How each factor affects the staining
Membrane topology	FCGR2A has extracellular residues 34–217, a transmembrane segment at 218–240, and a cytoplasmic region at 241–317 (UniProt P12318 topology). This supports a membrane expectation, but does not identify the antibody epitope or require a visibly crisp rim in paraffin IHC.
Cell and tissue context	High staining is reported in lung macrophages and endometrial ciliated epithelial cells; Medium staining occurs in bone marrow hematopoietic cells, splenic red pulp cells, and tonsillar non-germinal center cells (HPA: tissue IHC). Use cell identity when interpreting intensity; whole-section color is an inadequate substitute.
Evidence and antibody specificity	HPA rates tissue IHC Supported and notes medium consistency with RNA, unannotated stained structures, and antibodies that may target proteins from more than one gene (HPA: tissue IHC). HPA010718 and HPA014730 are individually Supported for IHC (HPA: antibodies). An unexpected stained cell therefore needs control review before attribution to FCGR2A.
ICC/IF localisation question	If asked where signal should appear in ICC/IF, HPA reports plasma membrane as supported and Golgi localisation as uncertain; it also cautions that the antibodies may target multiple genes (HPA: subcellular). This imaging evidence does not turn ICC/IF into an IHC-P protocol option or establish a tissue-section Golgi pattern.

Why is my staining missing, weak or wrong?
Situation	Likely cause	Next action
Known-positive lung macrophages are unstained.	Macrophages may be absent from the examined area, or the IHC run may have failed; HPA reports High staining in this cell population (HPA: lung).	Confirm the cells on the counterstained section, then check the positive control, antibody preparation, retrieval step, and detection run (general IHC practice). Do not infer a target-specific fixation effect from this result.
Signal is weak but confined to expected cells.	Intensity varies by population: bone marrow hematopoietic cells and splenic red pulp cells are Medium, whereas lung macrophages are High (HPA: tissue IHC).	Compare like cell types across sections and score intensity with the positive control from the same run. Keep weak, cell-restricted staining distinct from background (general IHC practice).
Nuclei carry the dominant stain.	Nuclear dominance does not match UniProt's membrane assignment or HPA's cytoplasmic tissue profile (UniProt P12318 topology; HPA: tissue IHC).	Inspect the negative control and counterstain, and repeat the detection check if the pattern persists (general IHC practice). Record the result as unresolved rather than assigning nuclear FCGR2A.
Bronchial respiratory epithelium stains strongly.	HPA reports that cell population as Not detected (HPA: bronchus). Cross-reactivity or endogenous detection activity is possible, but this observation alone does not identify the cause.	Check a matched negative control and examine the stain's cellular distribution (general IHC practice). Compare with expected positive cells; retain the HPA multi-gene antibody caution when interpreting any residual epithelial signal (HPA: tissue IHC).
Diffuse chromogen obscures cell boundaries.	Broad background can arise from nonspecific binding or detection chemistry (general IHC practice); it prevents comparison with HPA's cell-associated tissue pattern (HPA: tissue IHC).	Review blocking, washes, chromogen development, and the negative control (general IHC practice). Reassess the section only when individual cells can be distinguished.
Can ICC/IF localisation settle an ambiguous IHC section?	HPA supports plasma membrane localisation in ICC/IF but labels additional Golgi localisation uncertain and flags multi-gene antibody targeting (HPA: subcellular).	Use the ICC/IF result as context for the expected compartment, then judge the IHC section by its tissue cell pattern and IHC controls (HPA: tissue IHC; general IHC practice).

Source: UniProt P12318 Human Protein Atlas tissue Human Protein Atlas subcellular

Experiment evidence

IHC & IF images showing FCGR2A staining

IHC analysis of FCGR2A using anti-FCGR2A antibody (A01450-1). FCGR2A was detected in paraffin-embedded section of human lung cancer tissue. Heat mediated antigen retrieval was performed in citrate buffer (pH6, epitope retrieval solution) for 20 mins. The tissue section was blocked with 10% goat serum. The tissue section was then incubated with 1μg/ml rabbit anti-FCGR2A Antibody (A01450-1) overnight at 4°C. Biotinylated goat anti-rabbit IgG was used as secondary antibody and incubated for 30 minutes at 37°C. The tissue section was developed using Strepavidin-Biotin-Complex (SABC)(Catalog # SA1022) with DAB as the chromogen.

A01450-1 · IHCIHC analysis of FCGR2A using anti-FCGR2A antibody (A01450-1). FCGR2A was detected in paraffin-embedded section of human lung cancer tissue.

IHC analysis of FCGR2A using anti-FCGR2A antibody (A01450-1). FCGR2A was detected in paraffin-embedded section of mouse spleen tissue. Heat mediated antigen retrieval was performed in citrate buffer (pH6, epitope retrieval solution) for 20 mins. The tissue section was blocked with 10% goat serum. The tissue section was then incubated with 1μg/ml rabbit anti-FCGR2A Antibody (A01450-1) overnight at 4°C. Biotinylated goat anti-rabbit IgG was used as secondary antibody and incubated for 30 minutes at 37°C. The tissue section was developed using Strepavidin-Biotin-Complex (SABC)(Catalog # SA1022) with DAB as the chromogen.

A01450-1 · IHCIHC analysis of FCGR2A using anti-FCGR2A antibody (A01450-1). FCGR2A was detected in paraffin-embedded section of mouse spleen tissue. Heat

HPA · Cerebral cortexHuman Protein Atlas IHC, Cerebral cortex. Source: https://www.proteinatlas.org/ENSG00000143226-FCGR2A/tissue/cerebral+cortex#imid_2942004

HPA · ColonHuman Protein Atlas IHC, Colon. Source: https://www.proteinatlas.org/ENSG00000143226-FCGR2A/tissue/colon#imid_2941938

HPA · LiverHuman Protein Atlas IHC, Liver. Source: https://www.proteinatlas.org/ENSG00000143226-FCGR2A/tissue/liver#imid_2941931

HPA · KidneyHuman Protein Atlas IHC, Kidney. Source: https://www.proteinatlas.org/ENSG00000143226-FCGR2A/tissue/kidney#imid_2941932

HPA · ICC-IF HELHuman Protein Atlas immunofluorescence, HEL, antibody HPA010776; green = FCGR2A, blue = nucleus, red = microtubules.

← swipe / scroll for more images →

Real IHC / IF data behind the staining-pattern expectations in this section.

Sample controls for FCGR2A IHC & IF

🧪Run lung first and expect macrophages to stain (HPA: High in lung macrophages). Use adipose tissue as a negative comparator, scoring adipocytes specifically (HPA: Not detected in adipocytes); on the lung slide, cells outside the macrophage population should lack specific staining relative to the macrophages (HPA: High in lung macrophages).

Positive control tissue: Endometrium (Ciliated epithelial cells, HPA High)

Negative control tissue: Adipose tissue (HPA Not detected)

ICC-IF cell lines (HPA subcellular resource): HPA ICC-IF images show FCGR2A in HEL, THP-1, U2OS, with annotated localisation: Plasma membrane (supported) (HPA subcellular).

Technical controls: Include a no-primary, secondary-only control; a concentration-matched rabbit isotype control for the catalog antibody; and FCGR2A-knockout material as a biological negative if available (caption: rabbit primary; standard IHC practice). Block endogenous peroxidase and assess endogenous biotin when using the caption’s biotin-based DAB detection in lung tissue (caption: biotinylated secondary, SABC and DAB; standard IHC practice).

⚠️Feasibility: A target-specific fixation window or fixation effect is unreported, and the selected SKU caption does not state a fixative (caption: fixative not stated). The paraffin-section caption uses heat retrieval in citrate buffer at pH 6 for 20 minutes as a starting condition; whether retrieval is required has not been established (caption: heat-mediated retrieval). Paraffin IHC has a documented example, while the supplied evidence does not establish that frozen sections or IF are easier; lung macrophages may contain pigment that complicates chromogenic scoring (caption: paraffin-section IHC; HPA: ICC-IF images; standard IHC practice).

HPA tissue IHC evidence for FCGR2A

Comprehensive Human Protein Atlas IHC scoring per tissue (reliability: Supported — Medium consistency between antibody staining and RNA expression data. Caution, targets protein from more than one gene. Antibody staining in cells/structures not annotated, view images.). 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
Endometrium	Ciliated epithelial cells	High	Protein (IHC)	HPA →
Lung	Macrophages	High	Protein (IHC)	HPA →
Bone marrow	Hematopoietic cells	Medium	Protein (IHC)	HPA →
Spleen	Cells in red pulp	Medium	Protein (IHC)	HPA →
Tonsil	Non-germinal center cells	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 →
Appendix	Glandular cells	Not detected	Protein (IHC)	HPA →
Bronchus	Respiratory epithelial cells	Not detected	Protein (IHC)	HPA →
Cervix	Glandular cells	Not detected	Protein (IHC)	HPA →

Section 3

Advanced FCGR2A IHC Tips

Troubleshoot FCGR2A staining in paraffin section IHC by checking retrieval, cell identity, staining compartment and controls before interpreting signal.

What retrieval should I try first when FCGR2A staining is weak?

Start with heat-mediated citrate buffer at pH 6 for 20 minutes (A01450-1 IHC caption). The selected paraffin section example used 1 μg/mL primary antibody overnight at 4°C, so check those conditions before changing retrieval (A01450-1 IHC caption). If staining remains weak, compare a modestly adjusted heating time on serial sections while keeping the positive control and detection steps constant (standard IHC practice). Check tissue preservation and whether lung macrophages stain, since HPA reports high staining in that cell population (HPA: High in lung macrophages). Excessive retrieval can damage morphology, making cellular localisation harder to judge (standard IHC practice).

Could fixation explain absent FCGR2A staining in my paraffin sections?

Target-specific sensitivity to fixation is unknown: the selected paraffin section caption does not state a fixative (A01450-1 IHC caption). Record the fixative and processing history for each specimen, and compare sections processed together before assigning a weak result to FCGR2A biology (standard IHC practice). Check morphology and include a section containing an expected positive population, such as lung macrophages (HPA: High in lung macrophages). Run the documented citrate pH 6 retrieval for 20 minutes consistently across that comparison (A01450-1 IHC caption). If fixation histories differ, report the difference as a limitation because this evidence does not establish a FCGR2A-specific fixation effect.

Should FCGR2A look membranous or cytoplasmic in chromogenic sections?

FCGR2A is a cell membrane receptor with an extracellular region at residues 34–217, a transmembrane segment at 218–240 and a cytoplasmic region at 241–317 (UniProt P12318 topology). HPA describes mainly plasma membrane localisation, with additional Golgi localisation marked uncertain because its antibodies can target proteins from multiple genes (HPA subcellular). Its tissue IHC profile also describes cytoplasmic staining in hematopoietic cells and macrophages (HPA tissue IHC). Assess staining within identifiable cells rather than requiring a perfect membrane outline in every paraffin section (standard IHC practice). Diffuse staining in unrelated cells needs control comparison before interpretation (HPA tissue IHC: cross-gene caution).

How can epitope location and isoforms change the staining I see?

FCGR2A has 2 listed isoforms, but the supplied product caption does not identify its epitope or isoform coverage (UniProt P12318 isoforms; A01450-1 IHC caption). The receptor has extracellular residues 34–217 and cytoplasmic residues 241–317, so epitope mapping would clarify which side the antibody recognises (UniProt P12318 topology). Extracellular glycosylation sites occur at residues 97 and 178; phosphorylation sites are listed at 288 and 304 (UniProt P12318 modifications). Do not attribute an altered IHC pattern to a particular modification or isoform without epitope and specificity evidence. Compare cellular distribution and appropriate controls when evaluating an unexpected pattern (standard IHC practice).

How should I plan IF to investigate an ambiguous FCGR2A IHC pattern?

Use a separate IF experiment to colocalise FCGR2A with a validated marker of the expected cell population, such as macrophages in lung (HPA: High in lung macrophages). Choose fluorophores in channels with low tissue autofluorescence and inspect an unstained section in those channels before interpreting overlap (standard IF practice). The antibody epitope is unspecified, so compare nonpermeabilised and gently permeabilised conditions if testing access to an extracellular or cytoplasmic epitope, respectively (A01450-1 IHC caption; UniProt P12318 topology). Include single stain controls for channel bleed-through and interpret apparent Golgi signal cautiously because HPA marks that location uncertain (standard IF practice; HPA subcellular). The paraffin IHC caption supplies no IF fixation conditions (A01450-1 IHC caption).

How do I troubleshoot diffuse brown staining around FCGR2A-positive immune cells?

First compare the stained section with a no-primary control and inspect where the brown deposit lies relative to intact cells (standard chromogenic IHC practice). The selected example used 10% goat serum, a biotinylated secondary and streptavidin-biotin detection with DAB (A01450-1 IHC caption). Check peroxidase blocking and consider whether the biotin-based detection system contributes background; these are general workflow checks, not FCGR2A-specific effects (standard IHC practice). Review washing and primary concentration against the documented 1 μg/mL condition before increasing signal amplification (A01450-1 IHC caption). HPA warns that its tissue antibody staining may include proteins from more than one gene, so brown signal alone does not prove FCGR2A identity (HPA tissue IHC).

What should I score when comparing FCGR2A across paraffin sections? ⚠ ANSWER MARKED FOR VERIFICATION

Define the cell population and compartment before scoring: HPA reports high staining in lung macrophages and medium staining in bone marrow hematopoietic cells (HPA tissue IHC). For identifiable positive cells, report percent positive and staining intensity, or an H-score on a 0–300 scale; for dispersed infiltrates, report positive-cell density per mm² (standard IHC scoring practice). Normalise cell counts to analysed viable tissue area and, where relevant, report the proportion of positive cells within the chosen cell population (standard IHC practice). Apply the same staining threshold, sampling rule and exclusion of necrotic areas to every section (standard IHC practice). Record background separately because HPA notes possible cross-gene staining (HPA tissue IHC).

How can I distinguish true FCGR2A signal from artefact?

Look for staining in plausible cells, including lung macrophages, and compare it with a negative reference such as adipocytes, where HPA reports no detection (HPA tissue IHC). FCGR2A is a cell membrane receptor, although HPA tissue IHC describes cytoplasmic staining in hematopoietic cells and macrophages (UniProt P12318 topology; HPA tissue IHC). Treat signal restricted to section edges, necrotic material or a no-primary control as suspect, and check endogenous peroxidase activity when assessing DAB deposits (standard chromogenic IHC practice). Staining of an unexpected cell type or compartment calls for cell identification and an independent specificity check (standard IHC practice). HPA rates tissue staining as Supported but cautions that its antibodies may target proteins from multiple genes (HPA tissue IHC).

Boster reagents

Best FCGR2A / Low affinity immunoglobulin gamma Fc region receptor II-a IHC Antibodies

IHC images for A01450-1 show paraffin sections of human lung cancer, mammary cancer and placenta, and mouse spleen (catalog image captions); no IF image is supplied (catalog image fields).

Real IHC data

Anti-FCGR2A Antibody ®

Cat # A01450-1

View product →

A01450-1 has IHC images from human lung cancer, mammary cancer and placenta, and mouse spleen (catalog image captions). M01450 lists human reactivity and IHC as an application, but has no IHC image in the payload (catalog applications, reactivity and image fields).

Which to pick: Choose A01450-1 for paraffin-section IHC supported by its own images; its captions report citrate retrieval at pH 6 and 1 µg/ml primary antibody, but do not report the fixative (A01450-1 image captions). For cross-species work, A01450-1 lists human, mouse and rat reactivity, with pictured IHC evidence for human and mouse only; M01450 is a human-reactive monoclonal with IHC listed but no image supplied (catalog reactivity, clone, applications and image fields). Neither SKU lists IF/ICC validation, so there is no supported IF/ICC pick here (catalog applications and IF image fields).

Each figure is that product's own IHC / IF validation image from its datasheet.

References

UniProt Consortium. UniProt entry P12318 (FCG2A_HUMAN, Low affinity immunoglobulin gamma Fc region receptor II-a).
Human Protein Atlas. FCGR2A tissue IHC expression (reliability: Supported).
Human Protein Atlas. FCGR2A subcellular location (ICC-IF): Mainly localized to the plasma membrane. In addition localized to the Golgi apparatus. Caution: Based on antibodies targeting proteins from multiple genes..
Human Protein Atlas. FCGR2A antibody validation summary (3 antibodies).
The macrophage colony-stimulating factor 1 response signature in breast carcinoma. Clinical cancer research : an official journal of the American Association for Cancer Research 2009 — PMC2987696.
FCGR2A contributes to M2 macrophages polarization in HCC through IL-4/JAK/STAT6 axis. Translational oncology 2025 — PMC12177172.
Analysis of stromal signatures in the tumor microenvironment of ductal carcinoma in situ. Breast cancer research and treatment 2010 — PMC2976659.
Variations in stromal signatures in breast and colorectal cancer metastases. The Journal of pathology 2010 — PMC2935495.
PubMed PMID:2824655 — UniProt-cited evidence.
PubMed PMID:2529342 — UniProt-cited evidence.
PubMed PMID:16710414 — UniProt-cited evidence.