DPP8 Antibody

What is DPP8 and what cellular functions does it perform?

DPP8 (Dipeptidyl peptidase 8) is a serine protease that cleaves N-terminal dipeptides from proteins having a proline or alanine residue at position 2. It is expressed in various tissues including the brain, liver, and skin, with notably high expression in immune cells . DPP8 serves as a key inhibitor of caspase-1-dependent monocyte and macrophage pyroptosis in resting cells by preventing the activation of NLRP1 and CARD8 . It functions by sequestering the cleaved C-terminal part of NLRP1 and CARD8 in a ternary complex, thereby preventing their oligomerization and activation . While the dipeptidyl peptidase activity is required to suppress NLRP1 and CARD8, neither appears to be a direct substrate of DPP8, suggesting the existence of intermediate substrates required for NLRP1 and CARD8 inhibition .

What antibody types are available for DPP8 detection and what applications are they validated for?

DPP8 antibodies are available in multiple formats with different specifications:

When selecting an antibody, researchers should consider the specific application requirements and target species. For mouse-derived antibodies used in mouse tissue, Mouse-On-Mouse blocking reagents may be needed for IHC and ICC experiments to reduce background signal .

How should DPP8 antibodies be stored and handled to maintain optimal performance?

DPP8 antibodies require specific storage conditions to maintain their functionality. Generally, antibodies should be stored at -20°C for long-term storage . For conjugated antibodies like PE-labeled versions, storage at 4°C in the dark is recommended to prevent photobleaching . Most antibodies are formulated in PBS with preservatives such as 0.05% sodium azide . When working with these antibodies, it's advisable to aliquot them to avoid repeated freeze-thaw cycles that can degrade antibody quality. Always centrifuge antibody vials briefly before opening to collect the solution at the bottom of the tube, and handle with powder-free gloves to prevent contamination.

What is the optimal protocol for using DPP8 antibodies in Western blot analyses?

For optimal Western blot performance with DPP8 antibodies:

• Sample Preparation:

  • Prepare protein lysates from cells or tissues using RIPA buffer with protease inhibitors

  • Determine protein concentration using BCA or Bradford assay

  • Denature 20-50 μg of protein in Laemmli buffer at 95°C for 5 minutes

• Gel Electrophoresis and Transfer:

  • Separate proteins on 10% SDS-PAGE gel (DPP8 is approximately 100 kDa)

  • Transfer to PVDF membrane at 100V for 60-90 minutes in cold transfer buffer

• Immunodetection:

  • Block membrane with 5% non-fat milk in TBST for 1 hour at room temperature

  • Incubate with primary DPP8 antibody at recommended dilution (typically 1:1000-1:2000) overnight at 4°C

  • Wash 3× with TBST, 5 minutes each

  • Incubate with appropriate HRP-conjugated secondary antibody for 1 hour at room temperature

  • Wash 3× with TBST, 5 minutes each

  • Develop using ECL substrate and detect signal

For DPP8 antibodies, optimization of antibody concentration is critical as the recommended dilution varies between manufacturers and lots . When analyzing DPP8 in cells treated with inhibitors or under different activation conditions, researchers should look for both the full-length protein and potential cleavage products .

How can researchers validate the specificity of their DPP8 antibody?

Validating antibody specificity is crucial for reliable research outcomes. For DPP8 antibodies, implement these validation approaches:

• Positive and Negative Controls:

  • Use cell lines with known high DPP8 expression (e.g., immune cells) as positive controls

  • Include DPP8 knockout or knockdown cells as negative controls

• Multiple Detection Methods:

  • Compare results across different techniques (WB, IHC, IF)

  • Verify signal localization matches known DPP8 subcellular distribution

• Peptide Competition Assay:

  • Pre-incubate antibody with immunizing peptide before application

  • DPP8-specific signal should disappear or significantly decrease

• Molecular Weight Verification:

  • Confirm detection at the expected molecular weight (~100 kDa for full-length DPP8)

  • Be aware of potential splice variants or post-translational modifications

• Cross-Reactivity Assessment:

  • Test reactivity against related dipeptidyl peptidases (DPP4, DPP9) to ensure specificity

  • Note that some antibodies derived from immunogens within the first 50 amino acids of DPP8 may show specific binding patterns

• Orthogonal Validation:

  • Compare protein detection with mRNA expression using qPCR

What are the recommended protocols for immunohistochemistry with DPP8 antibodies?

For successful immunohistochemistry (IHC) using DPP8 antibodies:

• Tissue Preparation:

  • Fix tissues in 10% neutral buffered formalin for 24-48 hours

  • Process and embed in paraffin

  • Section at 4-6 μm thickness

  • Mount on positively charged slides

• Antigen Retrieval:

  • Deparaffinize and rehydrate sections

  • Perform heat-induced epitope retrieval using citrate buffer (pH 6.0) or EDTA buffer (pH 9.0)

  • Heat in a pressure cooker or microwave for 15-20 minutes

  • Cool to room temperature

• Staining Protocol:

  • Block endogenous peroxidase with 3% H₂O₂ for 10 minutes

  • Block non-specific binding with 5% normal serum from secondary antibody host species

  • Apply primary DPP8 antibody at recommended dilution (1:50-1:200 for HPA008706 )

  • Incubate overnight at 4°C or 1-2 hours at room temperature

  • Wash thoroughly with PBS/TBST

  • Apply appropriate HRP-polymer or secondary antibody system

  • Develop with DAB substrate

  • Counterstain with hematoxylin, dehydrate, clear, and mount

• Special Considerations:

  • When using mouse monoclonal antibodies on mouse tissues, employ Mouse-on-Mouse blocking reagents to reduce background

  • Include both positive control tissues (immune cells, brain, liver) and negative controls (primary antibody omitted)

  • Optimize antibody dilution and incubation times for each specific antibody and tissue type

How can DPP8 antibodies be used to investigate the CARD8 inflammasome activation pathway?

DPP8 antibodies are valuable tools for studying the mechanism of CARD8 inflammasome activation:

• Co-immunoprecipitation Studies:

  • Use DPP8 antibodies to immunoprecipitate protein complexes

  • Analyze interacting partners like CARD8, NLRP1, and associated proteins

  • Detect changes in complex formation following DPP8/9 inhibitor treatment

• Immunoblotting for Pyroptosis Markers:

  • Use DPP8 antibodies alongside antibodies against caspase-1, GSDMD, and IL-1β

  • Monitor cleavage of GSDMD into the pyroptotic p30 fragment in response to DPP8/9 inhibitors (e.g., VbP, compound 8j)

  • Compare resting vs. activated T cells, which show differential sensitivity to DPP8/9 inhibitors

• Proximity Ligation Assay (PLA):

  • Combine DPP8 antibodies with antibodies against CARD8 or NLRP1

  • Visualize and quantify endogenous protein-protein interactions

  • Track changes in interactions following inhibitor treatment

• Immunofluorescence Microscopy:

  • Track subcellular localization of DPP8 during inflammasome activation

  • Co-localize with CARD8, NLRP1, and other inflammasome components

  • Monitor translocation events during pyroptosis induction

Research has shown that DPP8/9 inhibitors activate the CARD8 inflammasome in lymphocytes, with T cells being particularly sensitive (IC₅₀ ~5 nM for VbP) . Intriguingly, while resting T cells undergo CARD8-mediated pyroptosis in response to DPP8/9 inhibition, activated T cells are completely resistant even at high inhibitor concentrations (>50 μM) .

What are the key considerations when using DPP8 antibodies to compare protein expression across different cell activation states?

When using DPP8 antibodies to study expression across different cell states:

• Standardized Sample Preparation:

  • Process all cellular samples simultaneously using identical protocols

  • Normalize protein loading precisely (validate with multiple housekeeping proteins)

  • Consider subcellular fractionation as DPP8 distribution may change with activation

• Quantification Approaches:

  • Use digital image analysis software for densitometry of Western blots

  • Employ flow cytometry with PE-conjugated DPP8 antibodies for single-cell quantification

  • Calculate relative expression ratios compared to standards across experiments

• Control for Cell Type-Specific Effects:

  • T cell sensitivity to DPP8/9 inhibitors varies dramatically with activation state

  • Resting T cells are highly sensitive (IC₅₀ ~5 nM for VbP), while activated T cells are completely resistant

  • This difference persists despite both cell states expressing the proteins required for CARD8-mediated pyroptosis

• Temporal Considerations:

  • Monitor DPP8 expression over time during cell activation

  • Correlate DPP8 levels with sensitivity to inhibitors and pyroptosis markers

  • Design time-course experiments to capture dynamic changes

• Species-Specific Variations:

  • T cell sensitivity to DPP8/9 inhibitors varies considerably between species

  • Use species-appropriate antibodies and validate cross-reactivity

  • Consider evolutionary conservation when comparing across species

How should researchers interpret conflicting DPP8 antibody data from different detection methods?

When faced with conflicting results from different detection methods:

• Evaluate Antibody Characteristics:

  • Compare epitope recognition sites between antibodies

  • Assess antibody clonality (monoclonal vs. polyclonal)

  • Review antibody validation data for each method

• Consider Protein Modifications and Interactions:

  • DPP8 undergoes N- and O-glycosylation that may affect epitope accessibility

  • Protein-protein interactions may mask antibody binding sites in certain contexts

  • Conformational changes might expose or hide epitopes in different assays

• Method-Specific Limitations:

  • Western blot detects denatured proteins, revealing all epitopes but losing conformation

  • IHC and IF detect proteins in their native environment but may be affected by fixation

  • Flow cytometry requires cell permeabilization for intracellular DPP8 detection

• Biological Context Matters:

  • DPP8 function changes with cell type and activation state

  • Although activated T cells express key proteins for CARD8-mediated pyroptosis, they are resistant to DPP8/9 inhibitors

  • This suggests post-translational modifications or inhibitors affecting DPP8 functionality

• Resolution Strategies:

  • Use multiple antibodies recognizing different epitopes

  • Employ genetic approaches (knockdown/knockout) as confirmation

  • Consider mass spectrometry-based proteomic analysis as an antibody-independent method

How should researchers design experiments to investigate DPP8's role in inflammasome regulation?

To effectively study DPP8's role in inflammasome regulation:

• Cell Model Selection:

  • Choose appropriate cell types based on research question

  • Primary human T cells show high sensitivity to DPP8/9 inhibitors in resting state (IC₅₀ ~5 nM)

  • Include multiple cell types as sensitivity varies (T cells > NK cells > B cells)

• Inhibitor Studies Design:

  • Use multiple DPP8/9 inhibitors with different potencies (VbP, compound 8j)

  • Include appropriate controls (vehicle, DPP4-specific inhibitors)

  • Construct dose-response curves covering a wide concentration range

  • Monitor time-dependent effects (short vs. long exposure)

• Readout Selection:

  • Cell viability assays (Cell-TiterGlo)

  • Flow cytometry (Annexin V/PI staining) to distinguish pyroptosis from apoptosis

  • Western blot for pyroptosis markers (GSDMD p30 fragment)

  • Microscopy for morphological changes

• Genetic Manipulation Approaches:

  • Use CRISPR/Cas9 to knockout DPP8, CARD8, or NLRP1

  • Create catalytically inactive DPP8 mutants to distinguish enzymatic from scaffolding functions

  • Employ inducible expression systems to control timing and level of protein expression

What controls are essential when performing DPP8 antibody-based research in immune cells?

When using DPP8 antibodies in immune cell research, include these critical controls:

• Antibody Validation Controls:

  • Primary antibody omission control

  • Isotype control at matching concentration

  • Blocking peptide competition assay

  • DPP8 knockdown/knockout cell lines

• Cell State Controls:

  • Paired resting and activated lymphocyte samples

  • Activated T cells are resistant to DPP8/9 inhibitors despite expressing CARD8 pathway components

  • Include both CD4⁺ and CD8⁺ T cells as they may respond differently

  • NK cells and B cells as comparison cell types with lower sensitivity

• Inhibitor and Treatment Controls:

  • Vehicle control (DMSO with 0.1% TFA for VbP to prevent cyclization)

  • Concentration gradient to establish dose-response

  • Time course to determine temporal dynamics

  • Selective inhibitors for related peptidases as specificity controls

• Cell Death Pathway Discrimination:

  • Caspase inhibitors (zVAD-FMK) to distinguish caspase-dependent processes

  • Specific inflammasome inhibitors (MCC950 for NLRP3)

  • Markers to distinguish pyroptosis from apoptosis:

    • GSDMD cleavage (pyroptosis) vs. PARP cleavage (apoptosis)

    • Annexin V⁺/PI⁺ (pyroptosis) vs. Annexin V⁺/PI⁻ (early apoptosis)

• Species Consideration Controls:

  • Human, mouse, and rat T cells show different sensitivities to DPP8/9 inhibitors

  • When using mouse-derived antibodies on mouse tissues, employ Mouse-on-Mouse blocking reagents

How can researchers effectively use DPP8 antibodies to investigate the differential sensitivity of resting versus activated T cells to DPP8/9 inhibitors?

To investigate the differential sensitivity phenomenon:

• Experimental Design Framework:

  • Isolate primary human T cells using negative selection

  • Divide cells into resting and activated conditions (using CD3/CD28 Dynabeads for 48h)

  • Treat both populations with DPP8/9 inhibitors at multiple concentrations

  • Assess viability, pyroptosis markers, and protein expression

• Antibody-Based Analysis Techniques:

  • Western Blot Analysis:

    • Compare DPP8, CARD8, caspase-1, and GSDMD levels and processing

    • Activated T cells show no GSDMD cleavage despite inhibitor treatment

    • Quantify expression differences using densitometry

  • Flow Cytometry:

    • Use PE-conjugated DPP8 antibodies for quantitative single-cell analysis

    • Combine with cell activation markers and viability dyes

    • Compare subcellular localization between cell states using imaging flow cytometry

  • Immunoprecipitation:

    • Pull down DPP8 complexes from resting vs. activated cells

    • Analyze differences in interacting partners

    • Investigate post-translational modifications that may explain resistance

• Key Comparison Points:

  • DPP8 expression levels between cell states

  • DPP8 subcellular localization

  • DPP8 protein interactions (especially with CARD8)

  • Post-translational modifications

  • Downstream signaling pathway components

• Mechanistic Investigation:

  • Create chimeric proteins between DPP8 and DPP9 to identify resistance-conferring domains

  • Use site-directed mutagenesis to modify potential regulatory sites

  • Employ phospho-specific antibodies to assess activation-induced phosphorylation

  • Investigate proteasome involvement using inhibitors like bortezomib

Research has established that activated T cells remain completely resistant to high doses (>50 μM) of VbP even after 24h exposure, while resting T cells are eliminated by nanomolar concentrations (IC₅₀ ~5 nM) . This striking difference presents an important model system for understanding regulation of inflammasome activation.

What are common issues when using DPP8 antibodies in Western blotting and how can they be resolved?

Technical tip: For DPP8 Western blotting, optimal dilutions should be experimentally determined for each antibody . Starting with a 1:1000 dilution in 5% BSA in TBST and overnight incubation at 4°C is recommended, followed by optimization as needed.

How can researchers minimize background when using DPP8 antibodies in immunofluorescence applications?

To achieve clean immunofluorescence staining with DPP8 antibodies:

• Fixation Optimization:

  • Test different fixatives (4% PFA, methanol, acetone)

  • Optimize fixation duration (10-20 minutes)

  • Fresh fixatives yield better results than stored solutions

• Blocking Strategies:

  • Use 5-10% serum from the same species as the secondary antibody

  • Add 0.1-0.3% Triton X-100 for permeabilization

  • Include 1% BSA to reduce non-specific binding

  • For mouse antibodies on mouse tissues, use specialized Mouse-on-Mouse blocking kits

• Antibody Dilution and Incubation:

  • Dilute DPP8 antibodies appropriately (start with 0.25-2 μg/mL for immunofluorescence)

  • Incubate overnight at 4°C in humid chamber

  • Use antibody diluent with background reducing components

• Washing Protocol:

  • Perform thorough washing (at least 3x5 minutes)

  • Use gentle agitation during washes

  • Ensure complete buffer removal between steps

• Controls and Countermeasures:

  • Include secondary-only controls

  • Use isotype controls at matching concentration

  • Perform peptide competition assays

  • Consider autofluorescence quenching agents for certain tissues

  • Optimize microscope settings to distinguish specific signal from background

• Signal Amplification Alternatives:

  • For weak signals, consider tyramide signal amplification

  • Try biotin-streptavidin systems for enhanced detection

  • Use directly conjugated antibodies to eliminate secondary antibody background

What strategies should be employed when DPP8 antibody results contradict functional assay outcomes?

When facing discrepancies between antibody detection and functional results:

• Revisit Antibody Validation:

  • Verify antibody specificity through additional controls

  • Test multiple antibodies targeting different DPP8 epitopes

  • Confirm results with non-antibody methods (e.g., mass spectrometry)

• Consider Post-Translational Modifications:

  • DPP8 undergoes N- and O-glycosylation that may affect function without altering detection

  • Investigate phosphorylation states that might regulate activity

  • Perform assays to detect protein conformational changes

• Examine Protein-Protein Interactions:

  • DPP8 functions in complexes with CARD8 and NLRP1

  • Presence of interaction partners may affect function without changing expression

  • Use co-immunoprecipitation to assess complex formation

• Analyze Subcellular Localization:

  • Changes in localization may affect function without altering total protein levels

  • Perform subcellular fractionation followed by Western blotting

  • Use confocal microscopy to track DPP8 distribution

• Resolve Activation-Related Discrepancies:

  • Resting and activated T cells show dramatically different responses to DPP8/9 inhibitors

  • This occurs despite both expressing the necessary proteins for CARD8-mediated pyroptosis

  • Investigate mechanisms of this resistance through detailed biochemical analysis

• Experimental Design Refinement:

  • Include appropriate time points (changes in function may precede detectable protein changes)

  • Control for cell heterogeneity through sorting or single-cell analysis

  • Design experiments to directly link DPP8 activity and expression

How might emerging antibody technologies enhance DPP8 research?

Emerging antibody technologies poised to advance DPP8 research include:

• Single-Domain Antibodies (Nanobodies):

  • Smaller size enables access to cryptic epitopes on DPP8

  • Superior penetration into tissue samples

  • Potential for intracellular expression to track DPP8 in live cells

  • Reduced cross-reactivity with other dipeptidyl peptidases

• Recombinant Antibody Fragments:

  • Fab and scFv fragments with consistent production quality

  • Engineered specificity for particular DPP8 conformations

  • Reduced background in imaging applications

  • Potential for site-specific conjugation of fluorophores or biotin

• Proximity-Based Labeling Antibodies:

  • Antibodies conjugated to enzymes like APEX2 or TurboID

  • Enable identification of DPP8 interactors in specific cellular compartments

  • Map DPP8 protein interaction networks in different cell activation states

  • Compare interactomes between resistant and sensitive cell populations

• Bifunctional Antibodies:

  • Dual specificity for DPP8 and interacting partners

  • Enhanced detection of transient interactions

  • Targeted degradation of DPP8 using proteolysis-targeting chimeras (PROTACs)

  • Forced proximity assays to investigate protein-protein interactions

• Conformation-Specific Antibodies:

  • Recognition of active vs. inactive DPP8 conformations

  • Detection of inhibitor-bound states

  • Monitoring conformational changes during inflammasome activation

  • Differentiating between resting and activated cell DPP8 structures

What are the most promising research questions regarding DPP8's role in inflammasome regulation that remain to be addressed?

Critical unresolved questions in DPP8 inflammasome research include:

• Mechanistic Understanding:

  • What are the endogenous substrates of DPP8 that mediate NLRP1 and CARD8 inhibition?

  • How does DPP8 enzymatic activity translate to inflammasome suppression?

  • What is the structural basis for DPP8/9 inhibitor recognition by CARD8?

• Cell-Type Specificity:

  • Why are T cells particularly sensitive to DPP8/9 inhibitors compared to other lymphocytes?

  • What factors determine the varying sensitivities across immune cell populations?

  • How do species differences in sensitivity arise, and what can they teach us?

• Activation State Resistance:

  • What molecular changes during T cell activation confer resistance to DPP8/9 inhibitors?

  • Does this resistance mechanism operate in other cell types?

  • Can the resistance mechanism be pharmacologically targeted?

• Physiological Relevance:

  • What endogenous signals regulate DPP8 activity in vivo?

  • Does DPP8-mediated inflammasome regulation contribute to immune homeostasis?

  • Are there pathological conditions where DPP8 dysfunction contributes to disease?

• Therapeutic Potential:

  • Can DPP8/9 inhibitors be developed as selective immunomodulatory agents?

  • Could targeting the DPP8-CARD8 axis provide novel approaches for inflammatory disorders?

  • How might the differential sensitivity of resting vs. activated T cells be exploited therapeutically?

Recent research has established that DPP8/9 inhibitors activate pyroptosis in resting lymphocytes through the CARD8 inflammasome, with T cells being particularly sensitive . The striking phenomenon that activated T cells become completely resistant to these inhibitors, despite expressing the necessary inflammasome components, presents an intriguing model system for understanding inflammasome regulation .