CD63 Antibody

What is CD63 and what cellular compartments can it be detected in?

CD63 is a 53 kDa type III lysosomal glycoprotein belonging to the tetraspanin (TM4SF) family. It is also known as LAMP-3, ME491, granulophysin, and TSPAN30 . CD63 is primarily localized in late endosomes and lysosomes, but redistributes to the plasma membrane upon cellular activation . Its expression pattern varies across cell types - it is abundant in activated platelets, monocytes, and macrophages, while being weakly expressed in resting granulocytes, T lymphocytes, and B lymphocytes . CD63 is also found in non-hematopoietic cells including endothelium, fibroblasts, osteoclasts, and smooth muscle cells .

For optimal detection of CD63 in different cellular compartments, consider these methodological approaches:

• For surface CD63: Flow cytometry with non-permeabilized cells

• For total CD63: Flow cytometry with fixed and permeabilized cells (paraformaldehyde fixation followed by saponin permeabilization works well)

• For subcellular localization: Immunofluorescence microscopy with co-staining for compartment-specific markers

What are the key applications of CD63 antibodies in research?

CD63 antibodies have diverse applications across multiple research areas:

When designing experiments, select antibodies validated for your specific application, as performance can vary between techniques .

How should I select the appropriate CD63 antibody for my experiment?

Selecting the optimal CD63 antibody requires consideration of multiple factors:

• Target species: Human CD63 shares 67% and 65% amino acid sequence identity with mouse and rat CD63, respectively . Some antibodies like clone H5C6 recognize human CD63 and cross-react with non-human primates .

• Application compatibility: Different antibody clones perform differently across applications. Review validation data for your specific application (WB, IHC, IF, FC) .

• Epitope recognition: Some antibodies target the large extracellular loop (LEL) of CD63, which is crucial for interactions with partners like HIV-1 gp41 . For functional studies, epitope location matters.

• Clone type: Monoclonal antibodies (e.g., H5C6, CLB-Gran/12) offer high specificity for a single epitope, while polyclonal antibodies may provide higher sensitivity by recognizing multiple epitopes .

• Format requirements: Consider whether you need conjugated antibodies (PE, FITC) for direct detection or unconjugated antibodies for flexibility in secondary detection systems .

Always pilot test multiple antibodies when beginning a new research direction with CD63.

What dilutions should I use for CD63 antibodies in different applications?

Optimal dilutions vary by antibody formulation, application, and sample type. Based on the search results, recommended ranges include:

For optimal results:

• Always titrate the antibody for your specific sample type and detection system

• Include appropriate isotype controls at the same concentration

• Consider signal amplification methods for low abundance targets

• Follow manufacturer's recommendations for storage and handling to maintain antibody activity

How can I verify the specificity of a CD63 antibody?

Verifying antibody specificity is critical for generating reliable data. Implement these methodological approaches:

• Positive and negative controls: Compare staining between:

  • Known CD63-positive cells (activated platelets, monocytes, melanoma cells)

  • CD63-negative or low-expressing cells (HEK293T cells have been used as negative controls)

• Genetic validation: Compare antibody staining in:

  • Wild-type cells versus CD63 knockdown/knockout cells

  • CD63-overexpressing cell lines (e.g., HEK293T/CD63 as mentioned in the search results)

• Molecular weight verification: In western blots, CD63 typically appears as a smear between 30-60 kDa (often around 50-53 kDa) due to variable glycosylation .

• Deglycosylation test: Treatment with N-glycanase yields a sharp band at 25 kDa, closer to the predicted molecular weight of 25.6 kDa .

• Multiple antibody comparison: Use antibodies recognizing different CD63 epitopes and compare staining patterns.

• Cross-validation with literature: Compare your results with published CD63 localization patterns for your cell type.

Remember that CD63 detection patterns will vary based on cell activation status, fixation methods, and detection systems.

How can CD63 antibodies be utilized to study exosome biogenesis and function?

CD63 is a canonical exosome marker that plays functional roles in exosome formation and cargo selection. To leverage CD63 antibodies for exosome research:

• Exosome isolation validation:

  • Use western blotting with CD63 antibodies to confirm exosome isolation

  • Include additional markers (CD9, CD81, HSP70) for comprehensive characterization

  • Compare CD63 levels across different isolation methods to optimize protocols

• Cargo selection studies:

  • Use CD63 antibodies for immunoprecipitation to identify cargo proteins that interact with CD63

  • Compare exosome content before and after CD63 knockdown/knockout

  • Investigate if CD63 antibody treatment affects cargo loading

• Exosome uptake tracking:

  • Label purified exosomes with fluorescently-conjugated CD63 antibodies

  • Use flow cytometry and microscopy to track cellular uptake

  • Compare uptake of CD63-positive versus CD63-depleted exosomes

• Functional blocking experiments:

  • Test if CD63 antibodies can block exosome-cell interactions

  • Assess impact on exosome-mediated signaling and phenotypic changes

• Tetraspanin web analysis:

  • Use proximity ligation assays (PLAs) to visualize CD63 interactions with other tetraspanins

  • Investigate how these interactions contribute to exosome composition

When interpreting results, remember that CD63's role in exosomes may be cell type-specific and context-dependent. Multiple tetraspanins have overlapping functions, so compensation mechanisms may exist in CD63-deficient conditions.

What role does CD63 play in viral pathogenesis and how can antibodies help investigate this?

CD63 is implicated in multiple aspects of viral infection, particularly for HIV-1. According to the search results, the large extracellular loop (LEL) of CD63 interacts with the gp41 transmembrane envelope protein of HIV-1 at the virological synapse (VS) where viral particles are transferred between cells .

Methodological approaches using CD63 antibodies to study viral pathogenesis include:

• Mapping virus-host protein interactions:

  • Proximity ligation assays (PLAs) can confirm interactions between CD63 and viral proteins like gp41

  • Co-immunoprecipitation with CD63 antibodies can identify viral binding partners

  • Structure-function studies can be performed using antibodies targeting specific CD63 domains

• Visualizing virus-induced cellular changes:

  • Immunofluorescence microscopy can track CD63 redistribution during infection

  • Live cell imaging with CD63 antibodies can monitor recruitment to the virological synapse

  • Super-resolution microscopy can provide detailed localization information

• Functional blocking studies:

  • CD63 antibodies can assess whether blocking CD63 affects viral entry, replication, or spread

  • As noted in the search results, "Anti-CD63 antibodies suppress IgE-dependent allergic reactions," suggesting potential for blocking viral processes dependent on CD63

• Mutational analysis:

  • Comparing antibody binding to wild-type versus mutant CD63 (e.g., mutations in the CCG motif that abrogated recruitment to the VS)

  • Correlating antibody epitope accessibility with functional outcomes in viral infection

This research area could yield insights for antiviral therapeutic development targeting host factors rather than viral components, potentially offering broader spectrum activity.

How do CD63 antibodies perform in cancer research applications?

CD63 has emerging roles in cancer biology, with expression patterns varying across cancer types. CD63 antibodies have proven valuable in multiple aspects of cancer research:

• Expression profiling in tumors:

  • IHC studies have detected CD63 in various cancers including lung cancer, melanoma, and epithelial carcinomas

  • CD63 was found to be identical to the ME491 antigen expressed by melanoma cells

  • The search results mention successful staining of human lung cancer tissue using the MAB50482 antibody at 0.3 μg/mL

• Correlation with clinical parameters:

  • CD63 antibodies enable quantification of expression levels for correlation with:

    • Tumor stage and grade

    • Metastatic potential

    • Patient prognosis

    • Treatment response

• Functional studies in cancer cells:

  • CD63 affects cellular processes relevant to cancer including:

    • Cell-matrix adhesion and migration

    • VEGFA signaling via regulating KDR/VEGFR2 internalization

    • Exosome formation and intercellular communication

• Targeting CD63-positive cancer cells:

  • The search results describe the CD63-1 aptamer with medium-high binding affinity (Kd ~100 nM) that specifically targets CD63-overexpressing cancer cells like MDA-MB-231 breast cancer cells

  • This moderate affinity may provide an advantage by preferentially targeting high-expression cancer cells while sparing normal cells with low CD63 expression

• CD63 as a cancer biomarker:

  • CD63 antibodies are used in liquid biopsy approaches to detect cancer-derived exosomes

  • Multiplex staining with CD63 and other markers can characterize tumor heterogeneity

Methodological considerations include selecting antibodies validated for specific cancer applications and optimizing staining protocols for each tumor type.

What are the best practices for using CD63 antibodies in flow cytometry?

Flow cytometry is a powerful technique for analyzing CD63 expression in single cells. For optimal results:

• Sample preparation optimization:

  • For surface CD63: Use live cells or gentle fixation without permeabilization

  • For total CD63: Fix cells with paraformaldehyde (PFA) and permeabilize with saponin or specialized buffers like FlowX FoxP3/Transcription Factor Fixation & Perm Buffer Kit

  • Cell detachment method matters: The search results note that trypsinization doesn't reduce CD63 epitope detection (mean fluorescence intensity was 87.00 for EDTA-detached cells vs. 110.51 for trypsin-detached cells)

• Antibody selection and titration:

  • Select flow cytometry-validated CD63 antibodies (e.g., H5C6 clone)

  • Titrate antibodies to determine optimal concentration

  • Include appropriate isotype controls at the same concentration

• Fluorochrome considerations:

  • For direct detection, use pre-conjugated antibodies (PE, FITC)

  • For amplified signal, use primary antibodies with fluorescent secondary antibodies

  • Consider spectral overlap when designing multicolor panels

• Controls and validation:

  • Use CD63-positive cells (e.g., activated platelets, MDA-MB-231) as positive controls

  • Include CD63-negative cells (e.g., some HEK293T lines) as negative controls

  • Consider fluorescence-minus-one (FMO) controls for multicolor panels

• Analytical approaches:

  • For activation studies: Compare CD63 mean fluorescence intensity before and after stimulation

  • For heterogeneous populations: Use CD63 in combination with lineage markers

  • For exosome analysis: Couple exosomes to beads for enhanced detection

The search results specifically mention successful detection of CD63 in PBMCs using flow cytometry with appropriate fixation and permeabilization for intracellular staining .

How can we distinguish between different functional states of CD63 using antibodies?

CD63 exists in multiple functional states depending on cellular activation, localization, post-translational modifications, and protein-protein interactions. Advanced approaches to distinguish these states include:

• Activation-state specific detection:

  • In platelets and granulocytes, CD63 translocates from granules to the cell surface upon activation

  • Surface vs. total CD63 staining can differentiate between resting and activated states

  • The CLB-Gran/12 clone was used as a CD63 reference antibody for studying activated cells

• Conformation-dependent antibodies:

  • Some antibodies recognize CD63 only in its non-reduced form , suggesting they detect conformation-dependent epitopes

  • Different antibody clones may preferentially bind distinct structural states of CD63

• Post-translational modification detection:

  • CD63 undergoes extensive glycosylation, affecting its apparent molecular weight (30-60 kDa)

  • Treatment with glycosidases can reveal the core protein (25 kDa)

  • Antibodies that differentially recognize glycosylated vs. deglycosylated forms can be used

• Protein complex analysis:

  • CD63 forms complexes with integrins, kinases, and other tetraspanins

  • Proximity ligation assays (PLAs) can detect specific CD63-partner interactions

  • Co-immunoprecipitation followed by western blotting can identify complex composition

• Subcellular localization:

  • Immunofluorescence with compartment markers can distinguish between:

    • Lysosomal CD63

    • Plasma membrane CD63

    • Exosomal CD63

  • Super-resolution microscopy can provide detailed localization information

These approaches enable researchers to connect specific CD63 states with distinct biological functions, providing deeper insights into tetraspanin biology across health and disease contexts.