Cleaved-MPO (A49) Antibody

What is Cleaved-MPO (A49) Antibody and what epitope does it recognize?

Cleaved-MPO (A49) Antibody is a rabbit polyclonal antibody that specifically recognizes the cleaved form of myeloperoxidase (MPO), particularly detecting the fragment of activated MPO 89k protein resulting from cleavage adjacent to A49 . This antibody targets the N-terminal region of human MPO, specifically binding to amino acids 40-120 .

Myeloperoxidase itself is a heme protein synthesized during myeloid differentiation that constitutes a major component of neutrophil azurophilic granules. The mature MPO is a tetramer composed of 2 light chains and 2 heavy chains, producing hypohalous acids central to neutrophil microbicidal activity . The cleaved form represents an activated state of the enzyme, making this antibody particularly valuable for studying neutrophil activation.

What applications have been validated for Cleaved-MPO (A49) Antibody?

The Cleaved-MPO (A49) Antibody has been extensively validated for specific research applications with standardized protocols:

Multiple manufacturers have confirmed these applications through quality control testing, as evidenced by Western Blot analysis of 293 cells shown in product documentation . No validated protocols for immunohistochemistry, immunocytochemistry, or flow cytometry applications were identified in the current literature, though researchers may develop custom protocols for these purposes.

What species reactivity has been confirmed for Cleaved-MPO (A49) Antibody?

Species reactivity varies slightly between manufacturers, with consistent data for human samples:

When working with non-human samples, preliminary validation experiments are strongly recommended to confirm specificity . The primary target is human myeloperoxidase (UniProt ID: P05164) .

What are the optimal storage and handling conditions for Cleaved-MPO (A49) Antibody?

To maintain antibody performance and stability, adhering to proper storage conditions is critical:

These conditions are consistently recommended across manufacturers and reflect standard practices for antibody preservation .

How can researchers verify the specificity of Cleaved-MPO (A49) Antibody in their experimental systems?

Validating antibody specificity is essential for generating reliable data. For Cleaved-MPO (A49) Antibody, implement this methodological workflow:

• Positive and negative cellular controls:

  • Positive controls: Activated neutrophils, 293 cells (as shown in validation data)

  • Negative controls: Cell lines lacking MPO expression

• Immunogen competition:

  • Pre-incubate antibody with excess immunogenic peptide (amino acids 40-120)

  • Apply to duplicate samples

  • Specific signal should be significantly reduced or eliminated

• Multiple detection methods:

  • Compare Western blot results with ELISA quantification

  • Verify molecular weight (expected 89 kDa band)

• Genetic validation approaches:

  • siRNA knockdown of MPO

  • CRISPR-Cas9 knockout cell lines

  • Compare signal between wild-type and modified cells

The antibody undergoes affinity purification using epitope-specific immunogen, which enhances specificity compared to crude serum preparations .

What methodological modifications are recommended for detecting cleaved MPO in complex biological samples?

When working with complex biological samples containing multiple cell types or potential cross-reactive proteins, consider these methodological refinements:

• Sample preparation:

  • For tissue homogenates: Include protease inhibitors to prevent ex vivo MPO cleavage

  • For neutrophil isolation: Minimize activation during purification (avoid temperature fluctuations, mechanical stress)

  • For serum/plasma: Use specialized extraction buffers to minimize matrix effects

• Signal enhancement strategies:

  • For Western blot: Consider signal amplification systems for low-abundance samples

  • For ELISA: Implement sandwich format with capture antibody targeting different MPO epitope

  • Optimize blocking reagents (5% BSA often superior to milk for phospho-specific antibodies)

• Removal of interfering components:

  • Pre-clear samples with protein A/G beads to remove endogenous immunoglobulins

  • For tissue samples, perform subcellular fractionation to enrich for MPO-containing components

  • Consider immunoprecipitation to concentrate target protein before analysis

• Cross-validation:

  • Compare results with enzymatic MPO activity assays

  • Verify with alternative antibodies targeting different epitopes

These approaches significantly improve signal-to-noise ratio in challenging sample types .

How does Cleaved-MPO (A49) Antibody compare with CAB-A49 antibody in terms of epitope recognition and specificity?

While both antibodies contain "A49" in their designation, they target completely different proteins and systems:

CAB-A49 belongs to the IGHV3-53-using mAb lineage isolated from convalescent COVID-19 patients and has reduced potency against Omicron variants compared to other antibodies in the same lineage . This comparison highlights the importance of carefully distinguishing between similarly named antibodies in the scientific literature.

What are the optimal experimental controls when using Cleaved-MPO (A49) Antibody for neutrophil activation studies?

Robust experimental design requires carefully selected controls:

• Negative controls:

  • Unstimulated neutrophils (minimal cleaved MPO)

  • Isotype control antibody at equivalent concentration

  • Secondary antibody-only control

  • MPO-deficient cells (if available)

• Positive controls:

  • Neutrophils activated with PMA (phorbol 12-myristate 13-acetate)

  • Neutrophils stimulated with bacterial components (LPS, fMLP)

  • Recombinant cleaved MPO protein (if available)

• Treatment controls:

  • MPO inhibitors (e.g., 4-aminobenzoic acid hydrazide)

  • NADPH oxidase inhibitors (e.g., DPI)

  • Neutrophil elastase inhibitors (to prevent MPO cleavage)

• Technical controls:

  • Loading controls for Western blot (β-actin, GAPDH)

  • Consistent cell numbers across experimental conditions

  • Time-course studies to capture dynamic changes in MPO cleavage

These controls allow researchers to distinguish specific antibody binding from background signal and confirm biological relevance of detected cleaved MPO .

How can researchers optimize Western blot protocols specifically for Cleaved-MPO (A49) Antibody?

Western blot optimization for Cleaved-MPO (A49) Antibody should focus on these key parameters:

• Sample preparation:

  • Use RIPA buffer supplemented with protease inhibitors

  • Include phosphatase inhibitors if studying activation mechanisms

  • Standardize protein loading (20-50 μg total protein per lane)

  • Avoid excessive heating (65°C for 5 minutes preferred over boiling)

• Gel electrophoresis:

  • 8-10% polyacrylamide gels provide optimal resolution for 89 kDa protein

  • Include molecular weight markers spanning 50-100 kDa range

  • Consider gradient gels for simultaneous analysis of cleaved and uncleaved forms

• Transfer conditions:

  • Semi-dry transfer: 15V for 30 minutes

  • Wet transfer: 30V overnight at 4°C

  • Use PVDF membrane for highest protein binding capacity

• Blocking and antibody incubation:

  • Block with 5% BSA in TBST (preferred over milk)

  • Primary antibody dilution: Start at 1:1000 and optimize

  • Incubation: Overnight at 4°C with gentle rocking

  • Secondary antibody: Anti-rabbit HRP at 1:5000 for 1 hour at room temperature

• Detection system:

  • Enhanced chemiluminescence recommended for highest sensitivity

  • Exposure time: Start with 30 seconds and adjust as needed

  • Consider digital imaging systems for accurate quantification

Western blot analysis of 293 cells has been successfully performed using these parameters, as documented in manufacturer validation data .

What technical challenges might researchers encounter when using Cleaved-MPO (A49) Antibody in ELISA applications?

When developing ELISA protocols with Cleaved-MPO (A49) Antibody, researchers should anticipate and address these common challenges:

• Epitope accessibility:

  • The linear epitope (amino acids 40-120) may be partially obscured in native conformation

  • Consider testing both direct coating and capture antibody approaches

  • Optimize coating buffer pH (try pH 7.4, 8.0, and 9.6) to enhance epitope exposure

• Antibody concentration optimization:

  • Begin with the recommended 1:10000 dilution

  • Perform checkerboard titration against known positive samples

  • Determine optimal signal-to-noise ratio rather than maximum signal

• Cross-reactivity in complex samples:

  • Pre-absorb samples with irrelevant proteins to reduce non-specific binding

  • Include additional blocking steps with irrelevant species IgG

  • Consider sample pre-clearing with protein A/G beads

• Standard curve development:

  • No commercially available cleaved MPO standard exists

  • Consider using activated neutrophil lysate as relative standard

  • Implement internal controls for plate-to-plate normalization

• Signal development:

  • TMB substrate provides excellent sensitivity for HRP-conjugated detection systems

  • Optimize development time (typically 5-15 minutes)

  • Stop reaction with 2N H₂SO₄ and read at 450nm with 570nm reference

These technical considerations will significantly improve assay reliability and reproducibility for quantitative analysis of cleaved MPO .

What is the relationship between MPO cleavage at A49 and neutrophil functional states?

MPO cleavage at alanine 49 (A49) represents a specific processing event with functional significance:

• Biosynthesis and processing:

  • MPO is initially synthesized as a single-chain precursor

  • Subsequent proteolytic processing produces mature MPO tetramer

  • Cleavage at A49 occurs during neutrophil activation

  • The resultant 89 kDa fragment represents functionally active MPO

• Correlation with neutrophil activation:

  • Resting neutrophils: Predominantly unprocessed MPO

  • Primed neutrophils: Partial MPO cleavage

  • Fully activated neutrophils: Significant accumulation of cleaved MPO (A49)

• Functional implications:

  • Cleaved form exhibits enhanced enzymatic activity

  • Associates with increased production of hypochlorous acid

  • Contributes to neutrophil extracellular trap (NET) formation

  • Potentially involved in tissue damage during inflammatory conditions

• Research applications:

  • Cleaved-MPO (A49) Antibody provides a direct marker of functionally activated neutrophils

  • Can distinguish between neutrophil presence and functional activation state

  • Valuable for studying neutrophil dynamics in inflammatory diseases

Understanding this relationship enables researchers to design more informative experiments for investigating neutrophil biology in various pathological conditions .

How can Cleaved-MPO (A49) Antibody be integrated into multiparameter flow cytometry panels?

While flow cytometry is not explicitly listed among validated applications in the product information, researchers may develop protocols for this purpose. Consider this methodological approach:

• Cell preparation:

  • Isolate neutrophils using density gradient centrifugation

  • Fix cells with 4% paraformaldehyde (10 minutes, room temperature)

  • Permeabilize with 0.1% saponin or commercial permeabilization buffer

• Antibody panel design:

  • Surface markers: CD15, CD16 (neutrophil identification)

  • Activation markers: CD11b, CD66b, CD62L

  • Intracellular targets: Cleaved-MPO (A49), other granule proteins

  • Viability dye: Near-IR or fixable viability dyes

• Staining protocol:

  • Surface staining: 30 minutes at 4°C before fixation

  • Blocking: 5% normal goat serum, 30 minutes at room temperature

  • Primary antibody: Cleaved-MPO (A49) at 1:500 dilution, 45 minutes at room temperature

  • Secondary antibody: Fluorophore-conjugated anti-rabbit IgG at manufacturer's recommended dilution

• Controls and compensation:

  • Single-stained controls for each fluorophore

  • Fluorescence-minus-one (FMO) controls

  • Isotype control for Cleaved-MPO (A49) Antibody

  • Unstimulated and PMA-stimulated neutrophils as biological controls

• Analysis strategy:

  • Gate on neutrophils (FSC/SSC, CD15+/CD16+)

  • Exclude dead cells

  • Compare cleaved MPO signal between experimental conditions

  • Correlate with surface activation markers

This approach would enable researchers to specifically identify neutrophils that have undergone activation and MPO cleavage while simultaneously assessing other activation parameters .

How can Cleaved-MPO (A49) Antibody contribute to studies of neutrophil-mediated tissue damage in inflammatory diseases?

Cleaved-MPO (A49) Antibody offers unique advantages for investigating neutrophil-mediated pathology:

• Distinguishing neutrophil presence from activation:

  • Total MPO antibodies detect all neutrophils regardless of activation state

  • Cleaved-MPO (A49) Antibody specifically identifies functionally activated neutrophils

  • Enables distinction between neutrophil recruitment and functional activation

• Methodological approaches:

  • Tissue immunohistochemistry: Localize activated neutrophils within damaged tissue

  • Western blot of tissue homogenates: Quantify relative levels of neutrophil activation

  • ELISA of biological fluids: Monitor neutrophil activation biomarkers

• Research applications:

  • Study temporal relationship between neutrophil activation and tissue injury

  • Evaluate therapeutic interventions targeting neutrophil function

  • Compare localization of activated neutrophils with damaged tissue regions

  • Correlate cleaved MPO levels with disease severity metrics

• Experimental models:

  • Acute lung injury

  • Ischemia-reperfusion injury

  • Autoimmune vasculitis

  • Inflammatory bowel disease

This approach provides mechanistic insights beyond simple neutrophil enumeration, supporting more nuanced understanding of neutrophil contributions to disease pathology .

What are the potential pitfalls in data interpretation when using Cleaved-MPO (A49) Antibody?

Researchers should be aware of these potential challenges in data interpretation:

• Ex vivo activation artifacts:

  • Sample collection and processing may artificially activate neutrophils

  • Control for processing time and temperature

  • Compare with immediately fixed samples when possible

• Cross-reactivity considerations:

  • Polyclonal nature may introduce some non-specific binding

  • Validate signal specificity with appropriate controls

  • Consider dual-staining approaches for confirmation

• False negatives:

  • Epitope masking in certain fixation conditions

  • Optimize fixation protocols for each application

  • Consider alternative detection methods for validation

• Quantitative limitations:

  • Western blot provides semi-quantitative results at best

  • Standardize loading and exposure conditions

  • Include calibration standards when possible

• Biological context:

  • MPO cleavage is one of multiple neutrophil activation markers

  • Integrate with other functional readouts for comprehensive assessment

  • Consider temporal dynamics of MPO processing

Addressing these considerations will strengthen data interpretation and enhance experimental reproducibility .

How does recent research on antibody sequencing inform our understanding of polyclonal antibodies like Cleaved-MPO (A49)?

Recent advances in antibody sequencing technology provide insights relevant to polyclonal antibodies:

• Antibody heterogeneity:

  • Polyclonal antibodies like Cleaved-MPO (A49) contain multiple clones

  • Recent research demonstrates that peripheral B cell sequencing may not represent the complete B cell receptor repertoire

  • Techniques combining mass spectrometry and B-cell sequencing can characterize polyclonal composition

• Methodological implications:

  • Different antibody clones within a polyclonal preparation may have distinct affinities

  • Batch-to-batch variability inherent to polyclonal production

  • De novo protein sequencing could potentially identify dominant clones

• Research applications:

  • Consider testing multiple lots for critical experiments

  • Monoclonal derivatives may provide more consistent results for certain applications

  • Recombinant antibody production based on sequence data may offer advantages

• Future directions:

  • Potential development of monoclonal versions with enhanced specificity

  • Recombinant production to reduce batch variability

  • Structure-based optimization of binding properties

These considerations reflect the evolving understanding of antibody technology and may inform future development of improved reagents for MPO research .

What comparative advantages does Cleaved-MPO (A49) Antibody offer over enzymatic MPO activity assays?

Researchers have multiple options for studying MPO, each with distinct advantages:

The antibody-based approach offers particular advantages for:

• Studies requiring cellular localization

• Analysis of archival or fixed samples

• Distinguishing between inactive and active forms of MPO

• Multiplexed analysis with other markers

Enzymatic assays maintain advantages for:

• Direct functional assessment

• Higher throughput quantification

• Potential for greater sensitivity in some applications

Combining both approaches provides complementary insights into MPO biology and neutrophil function .

What is the recommended protocol for optimizing signal-to-noise ratio when using Cleaved-MPO (A49) Antibody in Western blot applications?

To maximize specific signal while minimizing background:

• Blocking optimization:

  • Test multiple blocking agents (5% BSA, 5% milk, commercial blockers)

  • Extend blocking time to 2 hours at room temperature

  • Add 0.1% Tween-20 to blocking buffer

• Antibody dilution optimization:

  • Perform serial dilutions from 1:500 to 1:2000

  • Test each dilution on identical positive control samples

  • Select dilution providing best signal-to-background ratio

• Wash protocol refinement:

  • Increase wash volume (at least 10× membrane volume)

  • Extend wash duration (5× 5 minutes)

  • Add 0.2% Tween-20 to wash buffer to reduce non-specific binding

• Membrane selection:

  • PVDF typically provides better signal-to-noise than nitrocellulose

  • Low-fluorescence PVDF recommended for fluorescent detection systems

  • Pre-activate PVDF with methanol before transfer

• Detection system optimization:

  • For chemiluminescence: Use fresh substrate, optimize exposure time

  • For fluorescence: Select secondary antibodies with minimal spectral overlap

  • For colorimetric: Extend development time with monitoring

Following these systematic optimization steps has been demonstrated to significantly improve detection of the 89 kDa cleaved MPO band in complex samples .

How should researchers approach validation of Cleaved-MPO (A49) Antibody in species other than human?

While primarily validated for human samples, some manufacturers indicate potential cross-reactivity with mouse and rat samples . For validation in non-human species:

• Sequence homology assessment:

  • Compare amino acid sequences of human vs. target species MPO

  • Focus on the immunogen region (amino acids 40-120)

  • Predict potential cross-reactivity based on conservation

• Stepwise validation protocol:

  • Begin with positive control human samples alongside target species

  • Include negative controls lacking MPO expression

  • Test multiple sample types (neutrophils, tissue with known MPO expression)

  • Verify with alternative antibodies if available

• Application-specific considerations:

  • Western blot: Compare molecular weight with predicted species-specific MPO

  • ELISA: Establish detection limits with purified or recombinant protein

  • Include appropriate species-specific positive controls

• Reporting standards:

  • Document all validation steps

  • Include both positive and negative results

  • Specify exact experimental conditions

This methodical approach ensures reliable interpretation of results when extending the use of Cleaved-MPO (A49) Antibody to non-human experimental systems .

What strategies can mitigate batch-to-batch variability when working with Cleaved-MPO (A49) Antibody?

Polyclonal antibodies inherently exhibit some batch-to-batch variability. Implement these strategies to minimize its impact:

• Procurement planning:

  • Purchase sufficient quantity from single lot for entire study

  • Document lot numbers in experimental records

  • When possible, test multiple lots before initiating major studies

• Standardization approaches:

  • Create standard operating procedures for each application

  • Include consistent positive controls in every experiment

  • Normalize results to internal standards

• Calibration methods:

  • Perform titration curves for each new lot

  • Create standard samples that can be used across experiments

  • Consider using recombinant MPO for standardization

• Data normalization:

  • Express results relative to consistent controls

  • Consider using reference samples that are tested with each new lot

  • Document transformation methods in publications

• Alternative considerations:

  • For critical applications, consider monoclonal alternatives

  • Multiple antibody approach targeting different epitopes

  • Create laboratory reference standards

These approaches significantly reduce variability and enhance reproducibility in longitudinal studies .

How can researchers distinguish between non-specific binding and true cleaved MPO signal in their experiments?

Discriminating specific from non-specific signals requires systematic controls:

• Critical experimental controls:

  • Isotype control antibody at equivalent concentration

  • Pre-adsorption with immunogen peptide (competitive inhibition)

  • MPO knockout or knockdown samples if available

  • Secondary antibody-only controls

• Signal validation approaches:

  • Verify molecular weight (89 kDa) in Western blot applications

  • Confirm signal reduction following MPO inhibition

  • Compare pattern with alternative MPO antibodies

  • Test across multiple applications (WB, ELISA)

• Sample-specific considerations:

  • Increase blocking stringency for high-background samples

  • Pre-clear samples with protein A/G to remove endogenous immunoglobulins

  • Optimize detergent concentration in buffers

  • Include sample-matched negative controls

• Technical adjustments:

  • Increase antibody dilution (reduce concentration)

  • Extend washing steps

  • Reduce incubation temperature

  • Filter buffers to remove particulates

These methodological refinements should be systematically implemented and documented to ensure reproducible, specific detection of cleaved MPO .