RAB3B / Ras-related protein Rab-3B · IHC design guide

Design Immunohistochemistry for RAB3B

Plan RAB3B IHC-P around cytoplasmic staining in pancreatic islet cells, prostate glandular cells and gastrointestinal endocrine cells (HPA tissue IHC). The catalog antibody was used on formaldehyde-fixed paraffin sections at 1:25 (datasheet M09431 IHC-P); score staining by cell type.

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

Immunohistochemistry protocol sheet for RAB3B (IHC for RAB3B): expected localisation Cytoplasmic staining in endocrine and glandular cells (HPA tissue IHC), antibody M09431, validated IHC image, and IHC protocol steps — Printable **RAB3B** IHC protocol sheet — expected localisation Cytoplasmic staining in endocrine and glandular cells (HPA tissue IHC), antibody M09431, controls and protocol steps. Open the full RAB3B IHC guide →

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RAB3B 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 staining in endocrine and glandular cells (HPA tissue IHC)
	Staining pattern	Cytoplasmic staining in islet, prostate and gut endocrine cells (HPA tissue IHC)
	Antigen retrieval	Citrate pH 6 HIER, heat-mediated (datasheet M09431)
	Positive control ⓘ	Colon+4 more · see all
	Negative control ⓘ	Adipose tissue+4 more · see all

Important caveats

Reasons your staining may differ from the expected pattern.

	Fixation	Formaldehyde-fixed paraffin sections were used (datasheet M09431 IHC-P) (selected-SKU IHC image M09431)
	Caveat	Staining varies by cell type within positive tissues (HPA tissue IHC)
	Regulation	Expression regulation not annotated (UniProt)
	Isoform / epitope	No isoforms annotated; epitope restriction unreported (UniProt)

Section 1

Recommended RAB3B IHC & IF Protocols

The catalog antibody’s IHC-P protocol is followed by four published RAB3B IHC protocols (PMC11151598; PMC12831361; PMC2951179; PMC13357932).

Recommended immunohistochemistry (IHC-P) protocol parameters
Sample	Formaldehyde-fixed, paraffin-embedded tissue sections (datasheet M09431; sample unspecified)
Fixation	Image formalin-fixed; duration unreported (datasheet M09431); 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 (datasheet M09431); 20 min, 95–100 °C (standard)
Peroxidase block	3% H2O2, 10 min, room temperature (standard)
Blocking	10% normal serum of the secondary host, 30 min, room temperature (standard)
Primary antibody	Mouse monoclonal (clone 1543CT354.60.92) anti-RAB3B, 1:25 (datasheet M09431)
Primary incubation	1 hours at 37°C (datasheet M09431)
Detection	HRP-polymer secondary, DAB chromogen 5–10 min (standard)
Counterstain	Hematoxylin, blue, dehydrate and mount (standard)
Expected result	RAB3B-positive staining in endocrine cells of colon (HPA tissue IHC: High). HPA tissue profile: Cytoplasmic expression in pancreatic islet cells, glandular cells in prostate and enteroendocrine cells of the gastrointestinal tract. No signal in the no-primary control.

💡Decision noteStart with heat-mediated citrate retrieval at pH 6 (datasheet: M09431); two published protocols also use heated citrate buffer (PMC12831361; PMC13357932).

Section 2

What Is the Expected RAB3B Staining Pattern?

RAB3B is associated with the cell membrane and Golgi apparatus and has no transmembrane segment (UniProt P20337). In tissue IHC, expect cytoplasmic staining in pancreatic islet cells, prostate glandular cells, and gastrointestinal endocrine cells (HPA tissue IHC). HPA rates the tissue profile Enhanced: paired antibodies show similar staining, although staining and RNA expression have medium consistency (HPA tissue IHC).

What am I looking at on my slide?
Distinct cytoplasmic staining in pancreatic islet cells, prostate glandular cells, or gastrointestinal endocrine cells.	This matches the reported tissue profile (HPA tissue IHC). Score the relevant cells separately from surrounding tissue; their distribution matters as much as staining strength (standard IHC practice).
Predominantly nuclear staining, with little or no cytoplasmic signal in the expected cells.	A nuclear-only pattern is inconsistent with the reported cytoplasmic IHC profile and UniProt membrane and Golgi locations (HPA tissue IHC; UniProt P20337). Check controls and staining conditions before interpreting it as RAB3B.
Strong staining throughout an unexpected cell population, including cells reported as undetected.	For example, adipocytes in adipose tissue are reported as Not detected (HPA tissue IHC). Such staining warrants checks for antibody cross-reactivity or endogenous detection activity; appearance alone cannot distinguish them (standard IHC practice).
Diffuse color across cells and surrounding tissue, without a discernible cell pattern.	This is background rather than a convincing match to the cell-restricted HPA profile (HPA tissue IHC). Evaluate blocking, washes, antibody concentration, and detection controls as general IHC checks (standard IHC practice).
No staining in pancreatic endocrine cells or another reported high-staining population.	These cells are reported as High, so an absent signal makes the run difficult to interpret (HPA tissue IHC). Review the positive control, retrieval, antibody and detection steps before assigning a biological negative result (standard IHC practice).

💡Expected RAB3B appearanceA convincing positive shows distinct cytoplasmic staining in the expected endocrine or prostate glandular cells, potentially strong in populations rated High; diffuse background, nuclear-only staining, or broad staining in reported negative cells is suspect (HPA tissue IHC; standard IHC practice).

How each factor affects the staining
Which cells are suitable positive comparators?	Pancreatic endocrine cells, prostate glandular cells, and endocrine cells in colon, duodenum, rectum, and small intestine are rated High (HPA tissue IHC). Compare like cell populations within the section; an entire organ is not uniformly positive.
What does the antibody validation establish?	Two listed antibodies, HPA003159 and CAB023293, have Enhanced IHC status (HPA antibodies). This supports the reported profile, while HPA still describes only medium consistency with RNA expression (HPA tissue IHC).
How should subcellular location guide scoring?	HPA describes cytoplasmic tissue staining; UniProt lists cell membrane and Golgi locations without a transmembrane segment (HPA tissue IHC; UniProt P20337). The paraffin IHC result need not resolve those structures individually.
Does the IF/ICC image predict the paraffin IHC pattern?	No. HPA reports approved cell-junction localization by ICC-IF in U-251MG, while its tissue IHC profile is cytoplasmic in specified cell types (HPA subcellular; HPA tissue IHC). Interpret each assay against its own evidence.
Can processing or modification predict staining loss?	UniProt records no signal peptide, propeptide, or glycosylation sites, and lists several modified residues (UniProt P20337). Without an antibody epitope or target-specific fixation data, these annotations do not predict retrieval needs or staining sensitivity.

Why is my staining missing, weak or wrong?
Situation	Likely cause	Next action
A reported High cell population is unstained.	The positive control or a general IHC step may have failed; the slide alone cannot identify which step (HPA tissue IHC; standard IHC practice).	Check control staining, antibody identity and dilution, retrieval conditions, and detection reagents against the validated IHC procedure (standard IHC practice).
All tissue compartments show a faint, even deposit.	Nonspecific reagent binding, incomplete washing, or excess detection signal can obscure a cell-restricted pattern (standard IHC practice).	Review blocking and washes, titrate primary antibody within the validated procedure, and compare with a primary-antibody omission control (standard IHC practice).
Nuclei dominate the staining pattern.	Nuclear-only staining conflicts with the cytoplasmic tissue profile and annotated membrane and Golgi locations (HPA tissue IHC; UniProt P20337).	Check the positive control and antibody identity; reassess retrieval and detection conditions before scoring nuclear signal as specific (standard IHC practice).
Reported negative cells stain strongly.	Cross-reactivity or endogenous detection activity is possible; adipocytes in adipose tissue are reported as Not detected (HPA tissue IHC; standard IHC practice).	Compare the expected positive cells and a primary-antibody omission control; review blocking and detection controls (standard IHC practice).
Endocrine cells stain in one gastrointestinal specimen but not another.	HPA rates endocrine cells High in colon, duodenum, rectum, and small intestine, but Not detected in appendix (HPA tissue IHC).	Verify the tissue and cell type before treating the difference as assay failure; use a reported High population as the positive comparator (HPA tissue IHC).
A weak result is called negative despite no positive control.	Without a working positive comparator, low signal cannot be separated confidently from a staining failure (standard IHC practice).	Repeat or review the run with a reported High cell population and score only the relevant cells; HPA's tissue profile has medium RNA-staining consistency (HPA tissue IHC; standard IHC practice).

Source: UniProt P20337 Human Protein Atlas tissue Human Protein Atlas subcellular

Experiment evidence

IHC & IF images showing RAB3B staining

M09431 staining RAB3B in human pancreas sections by Immunohistochemistry (IHC-P -paraformaldehyde-fixed, paraffin-embedded sections). Tissue was fixed with formaldehyde and blocked with 3% BSA for 0. 5 hour at room temperature; antigen retrieval was by heat mediation with a citrate buffer (pH6). Samples were incubated with primary antibody (1/25) for 1 hours at 37°C. A undiluted biotinylated goat polyvalent antibody was used as the secondary antibody.

M09431 · IHCM09431 staining RAB3B in human pancreas sections by Immunohistochemistry (IHC-P -paraformaldehyde-fixed, paraffin-embedded sections). Tissue

HPA · Cerebral cortexHuman Protein Atlas IHC, Cerebral cortex. Source: https://www.proteinatlas.org/ENSG00000169213-RAB3B/tissue/cerebral+cortex#imid_1115264

HPA · ColonHuman Protein Atlas IHC, Colon. Source: https://www.proteinatlas.org/ENSG00000169213-RAB3B/tissue/colon#imid_1115198

HPA · LiverHuman Protein Atlas IHC, Liver. Source: https://www.proteinatlas.org/ENSG00000169213-RAB3B/tissue/liver#imid_1115199

HPA · KidneyHuman Protein Atlas IHC, Kidney. Source: https://www.proteinatlas.org/ENSG00000169213-RAB3B/tissue/kidney#imid_1115184

HPA · ICC-IF U-251MGHuman Protein Atlas immunofluorescence, U-251MG, antibody HPA003159; green = RAB3B, blue = nucleus, red = microtubules.

← swipe / scroll for more images →

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

Sample controls for RAB3B IHC & IF

🧪Run pancreas first: pancreatic endocrine cells are High for RAB3B (HPA: High in pancreatic endocrine cells). Use adipose tissue adipocytes as the negative tissue (HPA: Not detected in adipocytes); on the pancreas slide, examine adjacent cells outside the endocrine compartment as internal background comparators without assuming they are RAB3B-negative (HPA: High assignment is specific to pancreatic endocrine cells).

Positive control tissue: Colon (Endocrine cells, HPA High)

Negative control tissue: Adipose tissue (HPA Not detected)

ICC-IF cell lines (HPA subcellular resource): HPA ICC-IF images show RAB3B in U-251MG, with annotated localisation: Cell Junctions (approved) (HPA subcellular).

Technical controls: Include no-primary (secondary-only) and host-species- and clonality-matched nonimmune IgG controls, plus a RAB3B knockout specimen if available (standard IHC controls). Quench endogenous peroxidase and check for endogenous biotin in pancreas because the selected caption uses a biotinylated secondary antibody (selected M09431 tissue-IHC caption; standard chromogenic IHC practice).

⚠️Feasibility: A target-specific fixation window or fixation effect is unreported; the selected caption record lists the fixative as unreported (selected M09431 tissue-IHC caption record). The selected paraffin-section example uses heat retrieval in citrate buffer at pH 6, but does not establish that retrieval is required for every specimen (selected M09431 tissue-IHC caption). The supplied evidence does not establish that frozen sections or IF are easier; endogenous biotin may complicate the caption's biotin-based detection in pancreas (selected M09431 tissue-IHC caption; standard IHC practice).

HPA tissue IHC evidence for RAB3B

Comprehensive Human Protein Atlas IHC scoring per tissue (reliability: Enhanced — Medium consistency between antibody staining and RNA expression data. Paired antibodies with high similarity supports the protein profile.). Rows are taken directly from the HPA tissue chart — click any row's HPA link to view the source.

Positive expression · recommended positive controls

Tissue	Cell type	Level	Evidence	Source
Colon	Endocrine cells	High	Protein (IHC)	HPA →
Duodenum	Endocrine cells	High	Protein (IHC)	HPA →
Pancreas	Pancreatic endocrine cells	High	Protein (IHC)	HPA →
Placenta	Syncytiotrophoblasts - cell body	High	Protein (IHC)	HPA →
Prostate	Glandular cells	High	Protein (IHC)	HPA →

Undetected expression · recommended negative controls

Tissue	Cell type	Level	Evidence	Source
Adipose tissue	Adipocytes	Not detected	Protein (IHC)	HPA →
Appendix	Endocrine cells	Not detected	Protein (IHC)	HPA →
Bone marrow	Hematopoietic cells	Not detected	Protein (IHC)	HPA →
Breast	Adipocytes	Not detected	Protein (IHC)	HPA →
Bronchus	Respiratory epithelial cells	Not detected	Protein (IHC)	HPA →

Section 3

Advanced RAB3B IHC Tips

Troubleshoot chromogenic RAB3B IHC in paraffin sections by checking retrieval, cell identity, staining location and controls against the reported tissue pattern (HPA tissue IHC).

Which retrieval conditions should I try first for weak RAB3B staining?

Start with heat-mediated antigen retrieval in citrate buffer at pH 6 (datasheet M09431). For the same antibody, the pancreas IHC caption reports 3% BSA blocking for 30 minutes and primary antibody at 1:25 for 1 hour at 37°C (caption M09431). If staining remains weak, compare a slightly longer heat exposure with the original condition on adjacent sections, while watching for tissue damage or increased background (standard IHC practice). Keep detection and imaging settings matched across that comparison, and use pancreatic endocrine cells as an expected positive population (HPA: High in pancreatic endocrine cells; standard IHC practice).

Could fixation explain weak or uneven RAB3B staining?

RAB3B-specific sensitivity to fixation is unknown from the supplied evidence; do not infer it from its tissue distribution or molecular features (evidence scope: no comparative fixation data). For paraffin IHC, record fixative, fixation duration, section thickness and time before processing for each specimen so uneven staining can be investigated (standard IHC practice). Compare sections processed together and include a known positive tissue on the same run, such as pancreas with endocrine cells (HPA: High in pancreatic endocrine cells; standard IHC practice). If staining varies across a specimen, inspect morphology and section edges before attributing the pattern to RAB3B biology (standard IHC practice).

Should RAB3B appear at the membrane, in cytoplasm, or near the Golgi?

Interpret RAB3B staining at cellular resolution: UniProt places it at the cell membrane and Golgi, while HPA describes cytoplasmic expression in pancreatic islet cells (UniProt P20337 subcellular location; HPA tissue IHC). A concentrated perinuclear signal can therefore be compatible with a Golgi pattern, but chromogenic staining alone does not establish organelle identity (UniProt P20337 subcellular location; standard IHC practice). HPA also reports cell-junction localisation from ICC/IF, which provides a separate localisation observation to compare cautiously with tissue IHC (HPA subcellular). Score staining only in morphologically identifiable cells and check whether the same pattern recurs in an expected positive population (HPA tissue IHC; standard IHC practice).

How should unknown epitope placement affect RAB3B IHC optimisation?

The record lists 0 annotated isoforms and a mature RAB3B chain spanning residues 2–219, but it does not locate this antibody’s epitope (UniProt P20337). RAB3B has no transmembrane segment, so do not assign a luminal or extracellular epitope without antibody-specific mapping (UniProt P20337 topology; standard IHC practice). Reported modifications include phosphorylation at Thr-86, Ser-188 and Ser-190, and a methyl ester at Cys-219; their effect on this antibody’s staining is untested (UniProt P20337 modified residues; evidence scope). If retrieval changes staining, compare expected cell populations and morphology before interpreting the change as epitope exposure (HPA tissue IHC; standard IHC practice).

How can IF help assess RAB3B staining without conflating the two assays?

For a parallel IF assessment, multiplex RAB3B with a validated marker of the expected endocrine cell population and check whether positive cells coincide (HPA: High in pancreatic endocrine cells; standard IF practice). Choose a far-red fluorophore when tissue autofluorescence affects shorter wavelengths, and inspect unstained and no-primary controls using identical acquisition settings (standard IF practice). Because RAB3B has no transmembrane segment and its antibody epitope is unspecified, assess permeabilisation against the epitope’s membrane-facing side once that orientation is established (UniProt P20337 topology; evidence scope; standard IF practice). Compare IF localisation with the chromogenic IHC pattern cautiously; HPA reports cell-junction localisation in ICC/IF images (HPA subcellular; standard IHC/IF practice).

What should I check when RAB3B chromogenic staining is diffuse?

Run a no-primary control through the same secondary and chromogen steps to identify detection-system background (standard IHC practice). The selected pancreas caption used a biotinylated secondary antibody, so include an appropriate detection control when evaluating signal unrelated to primary-antibody binding (caption M09431; standard IHC practice). For a peroxidase and DAB workflow, check the peroxidase block, blocking conditions and wash stringency before raising primary-antibody concentration (standard IHC practice). Compare diffuse colour with the expected cellular pattern in pancreatic endocrine cells and prostate glandular cells, and inspect damaged tissue or section edges separately (HPA tissue IHC; standard IHC practice).

How should I quantify RAB3B IHC across tissue sections? ⚠ ANSWER MARKED FOR VERIFICATION

Define the target cell population before scoring: HPA reports high staining in pancreatic endocrine cells and prostate glandular cells, among other specified populations (HPA tissue IHC). Within that population, record percent positive cells and staining intensity, then calculate an H-score using 0–3 intensity grades if the scoring plan calls for it (standard IHC practice). Normalise counts or positive area to the number or area of eligible target cells, rather than the entire tissue section, and report that denominator (standard IHC practice). Apply identical thresholds to controls and study sections, and have scoring reviewed without knowledge of group assignment where feasible (standard IHC practice).

How can I distinguish plausible RAB3B positivity from artefact?

Look for reproducible staining in expected cells, including pancreatic endocrine cells, gastrointestinal endocrine cells and prostate glandular cells, with a plausible cellular distribution (HPA tissue IHC; UniProt P20337 subcellular location). RAB3B is reported at the cell membrane and Golgi, while HPA tissue IHC describes cytoplasmic expression in selected cells; no single chromogenic pattern proves specificity (UniProt P20337 subcellular location; HPA tissue IHC; standard IHC practice). Staining restricted to section edges, necrotic areas or morphologically unexpected cells warrants review against adjacent sections and controls (standard IHC practice). Exclude endogenous enzyme or detection-system signal with a no-primary control before calling weak colour true RAB3B expression (standard IHC practice).

Boster reagents

Best RAB3B / Ras-related protein Rab-3B IHC Antibodies

M09431 has real IHC-P data from human pancreas paraffin sections (M09431 IHC caption). Its listed reactivity covers human, mouse, and rat (catalog: reactivity); no IF data are supplied (catalog: applications, IF images).

Real IHC data

Anti-RAB3B Antibody

Cat # M09431

View product →

M09431 is listed for IHC-P and shows staining in human pancreas paraffin sections (catalog: applications; M09431 IHC caption). It is listed as reactive with human, mouse, and rat, but the supplied IHC image documents human tissue only (catalog: reactivity; M09431 IHC caption).

Which to pick: For tissue IHC, choose M09431, a mouse monoclonal listed for IHC-P at 1:25 with an image from human pancreas paraffin sections (catalog: host, clone, applications, dilution; M09431 IHC caption). For IF/ICC, no listed SKU has an IF/ICC application or figure; M09431 would need independent validation (catalog: applications, IF images). For cross-species work, M09431 lists human, mouse, and rat reactivity, while its supplied IHC evidence covers only human pancreas sections; the caption reports paraformaldehyde-fixed paraffin sections and also describes formaldehyde fixation (catalog: reactivity; M09431 IHC caption).

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

References

UniProt Consortium. UniProt entry P20337 (RAB3B_HUMAN, Ras-related protein Rab-3B).
Human Protein Atlas. RAB3B tissue IHC expression (reliability: Enhanced).
Human Protein Atlas. RAB3B subcellular location (ICC-IF): Localized to the cell junctions..
Human Protein Atlas. RAB3B antibody validation summary (2 antibodies).
Rab3B enhances the stabilization of DDX6 to promote lung adenocarcinoma aggressiveness. Molecular medicine (Cambridge, Mass.) 2024 — PMC11151598.
Discovery and validation of RAB3B as a diagnostic biomarker for prostate cancer with serum PSA below 10 ng/mL based on a multi-omics study. Cancer cell international 2025 — PMC12831361.
In vitro expression of NGN3 identifies RAB3B as the predominant Ras-associated GTP-binding protein 3 family member in human islets. The Journal of endocrinology 2010 — PMC2951179.
Integrative genomic and functional analysis of RAB3B in lung adenocarcinoma: associations with m6A modification and ceRNA networks. Frontiers in pharmacology 2026 — PMC13357932.
PubMed PMID:2501306 — UniProt-cited evidence.
PubMed PMID:16710414 — UniProt-cited evidence.
PubMed PMID:15489334 — UniProt-cited evidence.