MUR4 Antibody

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Description

Definition and Context

Anti-Mur antibodies target the Mur antigen, a glycophorin variant associated with the MNS blood group system. These antibodies are often linked to GP.Mur (glycophorin Mur), a hybrid protein formed by recombination between GYPA and GYPB genes . Similarly, anti-Mi(a) antibodies target the Mi(a) antigen, a Miltenberger subclass antigen expressed on red blood cells (RBCs) . Both antibodies are clinically relevant due to their association with hemolytic transfusion reactions (HTR) and HDN.

Key Features of Anti-Mur and Anti-Mi(a) Antibodies

PropertyAnti-Mur AntibodyAnti-Mi(a) Antibody
Antigen TargetGP.Mur (glycophorin variant)Mi(a) antigen (MNS system)
Primary IsotypeIgG or IgM/IgG mix IgG or IgM/IgG mix
Saline ReactivityOften weak Often weak
Clinical SignificanceSevere HTR/HDN HDN and mild-moderate HTR

Note: Both antibodies exhibit cross-reactivity due to shared epitopes on glycophorin variants .

Prevalence in Populations

RegionMur Antigen FrequencyMi(a) Antigen FrequencyAnti-Mur Antibody PrevalenceAnti-Mi(a) Antibody Prevalence
Southern China6.4% 6.5% 0.65% 0.45%
Taiwan~7.3% N/AN/AN/A
CaucasiansRareRareRareRare

Clinical Outcomes

  • Anti-Mur Antibodies:

    • Severe HDFN: Phagocytic efficiency >80% in monocytes when antibody titers exceed 64 .

    • HTR: Associated with hemolysis in recipients with anti-Mur alloantibodies .

  • Anti-Mi(a) Antibodies:

    • HDN: Linked to hydrops fetalis and fetal death .

    • HTR: Mild-to-moderate reactions, especially in patients with chronic liver disease .

Flow Cytometry Assays for Clinical Significance

A phagocytosis assay using flow cytometry (FCM) demonstrated:

Antibody TiterPhagocytic EfficiencyClinical Outcome
<8<13%No adverse outcomes
8–6413–80%Progressive hemolysis risk
>64~80%Severe HDFN/hydrops fetalis

This assay helps predict the clinical impact of anti-Mur antibodies .

Genetic and Serological Correlations

  • GP.Mur Identification:

    • Genotyping (PCR-sequencing) identifies GP.Mur carriers with higher sensitivity than serology .

    • Serological screening using Mi(a)+ RBCs detects ~67% of GP.Mur carriers .

Antibody-Specific Challenges

  • Cross-Reactivity: Anti-Mi(a) may react with GP.Mur due to shared epitopes .

  • Screening Limitations: Commercial panels often lack GP.Mur/Mi(a)+ cells, leading to missed antibodies .

Research Gaps and Future Directions

  1. Standardization: Limited availability of GP.Mur/Mi(a)+ RBCs for antibody screening .

  2. Mechanistic Studies:

    • Role of IgG subclass (e.g., IgG1 vs. IgG4) in hemolysis .

    • Impact of hinge-region modifications (e.g., S228P) on antibody activity .

  3. Therapeutic Antibodies: No therapeutic monoclonal antibodies targeting Mur/Mi(a) are listed in major databases (e.g., ).

Product Specs

Buffer
Preservative: 0.03% Proclin 300
Constituents: 50% Glycerol, 0.01M Phosphate Buffered Saline (PBS), pH 7.4
Form
Liquid
Lead Time
Made-to-order (14-16 weeks)
Synonyms
MUR4 antibody; At1g30620 antibody; T5I8.7UDP-arabinose 4-epimerase 1 antibody; EC 5.1.3.5 antibody; UDP-D-xylose 4-epimerase 1 antibody
Target Names
MUR4
Uniprot No.

Target Background

Function
This antibody acts as a UDP-D-xylose 4-epimerase. However, it lacks both UDP-D-glucose and UDP-D-glucuronic acid 4-epimerase activities in vitro.
Database Links

KEGG: ath:AT1G30620

STRING: 3702.AT1G30620.1

UniGene: At.20201

Protein Families
NAD(P)-dependent epimerase/dehydratase family
Subcellular Location
Golgi apparatus, Golgi stack membrane; Single-pass type II membrane protein.
Tissue Specificity
High expression in roots. Also found in leaves, stems, flowers, and siliques.

Q&A

What are Mur antigens and how do they relate to MUR4 antibody research?

Mur antigens belong to a blood group system that has significantly higher frequency in Asian populations compared to Caucasian populations. The MUR4 antibody specifically targets these antigens. Research has demonstrated that Mur antigens and their corresponding antibodies have a high frequency in Southern China, with positive rates of Mur antigens reaching 6.4% among blood donors in this region . Understanding the properties and distribution of these antigens provides the foundation for MUR4 antibody development and application in both research and clinical settings.

What methods are most reliable for detecting Mur antigens in research samples?

For research purposes, routine serological microplate methods remain the gold standard for Mur antigen detection. According to comprehensive studies, these methods offer reliable detection with sufficient sensitivity for research applications . When implementing this approach:

  • Use standardized microplate formats with appropriate controls

  • Ensure proper sample preparation to avoid interference

  • Maintain consistent incubation conditions for reproducible results

  • Consider validation with monoclonal antibodies against Mia antigens, as they can predict the presence of Mur antigens due to their high correlation in expression patterns on red blood cells

This methodological approach allows researchers to reliably detect Mur antigens in diverse sample types, enabling consistent experimental outcomes.

How do researchers distinguish between anti-Mur and anti-Mia antibodies in experimental settings?

In experimental settings, distinguishing between anti-Mur and anti-Mia antibodies requires careful analysis of their serological properties and binding patterns. Research indicates that most anti-Mur and anti-Mia antibodies in positive patients are either IgM or IgM+IgG mixed types with saline activity . To differentiate between these antibodies:

  • Implement parallel testing with known Mur-positive and Mia-positive control cells

  • Analyze antibody binding at different temperatures (room temperature vs. 37°C)

  • Evaluate antibody reactivity in different media (saline vs. enhancement media)

  • Assess the strength of agglutination patterns

The correlation between Mur and Mia antigens expression on red blood cells provides an additional approach, where monoclonal antibodies against Mia can predict the presence of Mur antigen, suggesting a methodological strategy for indirect identification .

How should researchers design experiments to evaluate MUR4 antibody specificity and cross-reactivity?

Designing robust experiments to evaluate MUR4 antibody specificity requires multiple complementary approaches:

  • Antigen panel testing: Include Mur-positive, Mia-positive, and negative controls in all experiments

  • Cross-adsorption studies: Pre-adsorb antibodies with related antigens to assess specific binding

  • Competitive binding assays: Use known ligands to evaluate binding site specificity

  • Flow cytometry validation: Implement multi-parameter flow cytometry to quantify binding to different cell types

Research demonstrates significant correlation between Mur and Mia antigen expression, necessitating careful experimental controls to distinguish specific from cross-reactive binding . When analyzing results, consider that the incidence of anti-Mur (0.65%) and anti-Mia (0.45%) varies between populations, with significant differences between blood donors and patients .

What methodological approaches can optimize MUR4 antibody affinity without compromising specificity?

Recent advances in antibody engineering offer several methodological approaches to optimize MUR4 antibody affinity while maintaining specificity:

  • Sequence-based design: Utilize computational platforms like DyAb for predicting antibody properties in low-data regimes

  • Edit distance optimization: Generate and test combinations of affinity-improving mutations while maintaining limited edit distance (ED ≤ 7) from the original sequence to preserve natural-like characteristics

  • Iterative testing and refinement: Implement genetic algorithms to sample design space efficiently, followed by experimental validation of top-ranked designs

Research demonstrates that this approach can produce antibodies with significantly improved affinity. For example, DyAb-designed antibodies achieved expression and binding rates exceeding 85%, comparable to single point mutants, with most designs improving upon the affinity of the lead molecule . The methodological workflow involves:

  • Identifying individual mutations that improve affinity

  • Generating combinations of these mutations

  • Using computational models to score designs

  • Experimental testing of top candidates

  • Incorporating data back into the training set for subsequent design rounds

How can researchers effectively humanize MUR4 antibodies while preserving antigen binding properties?

Humanization of MUR4 antibodies requires careful preservation of key binding residues while replacing non-human framework regions. The BioPhi platform provides a systematic methodological approach:

  • CDR grafting with minimal essential framework preservation: Identify and retain only critical framework residues that support CDR conformation

  • OASis-based humanness evaluation: Assess humanness using peptide analysis across prevalence thresholds from the Observed Antibody Space database

  • Iterative optimization: Balance humanness scores against binding properties through multiple design cycles

Research demonstrates that humanized antibodies can maintain binding properties while significantly reducing immunogenicity potential. The OASis identity method effectively differentiates between human, humanized, chimeric, and murine sequences, with clear statistical differences between groups (p<1e-8) . When implementing humanization:

  • Preserve all CDRs completely

  • Identify essential framework residues through structural analysis

  • Select appropriate human germline templates

  • Monitor humanness scores throughout the design process

  • Validate binding of humanized variants experimentally

How do differences in Mur antigen frequency across populations impact research sample selection and data interpretation?

Population differences in Mur antigen frequency create important methodological considerations for research design and data interpretation:

PopulationMur Antigen Positive RateAnti-Mur Incidence
Southern China (Blood Donors)6.4%0.65%
Asian populations (general)HigherVariable
Caucasian populationsSignificantly lowerRare

These population differences necessitate stratified sampling approaches and careful data interpretation . Methodologically, researchers should:

  • Include population diversity in research cohorts

  • Stratify data analysis by ethnic background

  • Report population characteristics in all publications

  • Consider regional differences when designing multi-center studies

Data from Southern China indicate no significant difference between Mur and Mia antigen frequencies (6.4% vs 6.5%, P>0.05), but significant differences exist in antibody incidence between blood donors and patients (P<0.05) . These findings underscore the importance of appropriate control selection and data stratification in experimental design.

What are the molecular mechanisms underlying the correlation between Mur and Mia antigen expression, and how do these impact antibody development?

The high correlation between Mur and Mia antigen expression on red blood cells presents both challenges and opportunities for antibody development. At the molecular level, these antigens share structural similarities while maintaining distinct epitopes. Research demonstrates that monoclonal antibodies against Mia can predict the presence of Mur antigen , suggesting:

  • Overlapping or adjacent epitope presentation

  • Shared regulatory mechanisms controlling expression

  • Common molecular pathways for biosynthesis and cell surface presentation

This correlation enables methodological approaches that leverage one antigen to study the other. For MUR4 antibody development, researchers can:

  • Use Mia-positive cells for preliminary screening

  • Develop dual-specificity antibodies that recognize conserved epitopes

  • Target unique determinants for specificity when needed

  • Implement competitive binding assays to distinguish between the antigens

Understanding these molecular relationships is crucial for designing antibodies with precise specificity profiles and interpreting experimental outcomes correctly.

How can deep learning models improve MUR4 antibody design and optimization for challenging research applications?

Deep learning approaches offer powerful methodological solutions for MUR4 antibody optimization, particularly in challenging research applications with limited training data:

  • Sequence-pair modeling: Leverage models like DyAb that predict property differences between sequence pairs rather than absolute properties

  • Transfer learning from large antibody datasets: Utilize pre-trained models on comprehensive antibody databases like the Observed Antibody Space (OAS)

  • Transformer architecture integration: Implement attention-based mechanisms similar to those used in natural language processing for protein sequence analysis

Research demonstrates these approaches can generate novel antibody variants with enhanced properties using limited training data (~100 labeled sequences) . The methodological workflow involves:

  • Training models on available sequence-property pairs

  • Generating and scoring novel sequence variants

  • Experimental testing of top candidates

  • Iterative improvement through data incorporation

For example, DyAb-designed antibodies achieved expression and binding rates exceeding 85%, with most designs improving upon the affinity of the lead molecule . This approach is particularly valuable for MUR4 antibody research where experimental data may be limited due to the specialized nature of the antigen.

What factors most commonly affect MUR4 antibody binding reproducibility, and how should researchers address them?

Several factors can impact MUR4 antibody binding reproducibility in research settings:

  • Antigen density variation: Mur antigen expression levels can vary between samples and cell types

  • Antibody lot-to-lot consistency: Production variations can affect binding characteristics

  • Experimental conditions: Temperature, pH, and buffer composition influence binding kinetics

  • Sample handling: Storage conditions and freeze-thaw cycles can degrade both antibodies and antigens

To address these factors methodologically:

  • Implement standardized protocols for sample preparation and storage

  • Include internal controls in every experiment

  • Characterize each antibody lot before experimental use

  • Maintain consistent experimental conditions across studies

  • Document all procedural details to enable reproducibility

Research on anti-Mur and anti-Mia antibodies indicates they are predominantly IgM or IgM+IgG mixed types with saline activity , suggesting they may be particularly sensitive to experimental conditions that affect multivalent binding.

How can researchers distinguish between true anti-Mur reactivity and non-specific binding in complex biological samples?

Distinguishing specific from non-specific binding requires rigorous methodological approaches:

  • Absorption controls: Pre-absorb samples with Mur-negative cells to remove non-specific reactivity

  • Competitive inhibition: Use purified antigens or specific peptides as competitive inhibitors

  • Multiple detection methods: Confirm results using orthogonal techniques (e.g., flow cytometry, ELISA, immunoprecipitation)

  • Titration analysis: Evaluate binding across antibody dilutions to assess affinity characteristics

When implementing these approaches, consider that the high correlation between Mur and Mia antigens necessitates careful control selection. Research indicates that in southern China, the incidence of anti-Mur and anti-Mia antibodies is 0.65% and 0.45% respectively , requiring appropriate positive and negative controls from relevant populations.

What quality control metrics should be implemented when validating new batches of MUR4 antibodies for research applications?

Comprehensive quality control for MUR4 antibodies should include:

Quality Control ParameterAcceptance CriteriaMethodological Approach
Specificity>95% binding to Mur+ vs. Mur- cellsFlow cytometry differential binding
SensitivityDetection at ≤1 μg/mLTitration analysis
Lot-to-lot consistency<15% variation in bindingComparative analysis with reference standard
Stability<10% activity loss over storage periodAccelerated stability testing
Cross-reactivity<5% binding to non-target antigensPanel screening

Additionally, humanness evaluation using methods like OASis identity can provide important quality metrics for antibodies intended for translational research. This approach analyzes 9-mer peptides across the antibody sequence against the Observed Antibody Space database, producing scores that effectively differentiate between antibodies of different origins (p<1e-8) .

How might advances in antibody repertoire analysis inform next-generation MUR4 antibody development?

The emergence of large-scale antibody repertoire databases presents transformative opportunities for MUR4 antibody research:

  • Natural diversity mining: The Observed Antibody Space (OAS) database contains over 500 million human sequences from more than 500 human subjects , enabling identification of naturally occurring anti-Mur binding motifs

  • Developability prediction: Natural human antibodies demonstrate developability properties comparable to clinical monoclonal antibodies , providing templates for engineered variants

  • Human-like sequence generation: Deep learning models trained on these repertoires can generate diverse libraries with favorable profiles

Methodologically, researchers can:

  • Search repertoire databases for sequences with Mur-binding motifs

  • Analyze CDR configurations across multiple anti-Mur antibodies

  • Identify conserved structural elements that determine specificity

  • Generate synthetic libraries based on natural sequence patterns

These approaches leverage the collective immune experience captured in repertoire data to accelerate MUR4 antibody development and optimization.

What computational approaches show the most promise for predicting MUR4 antibody immunogenicity and optimizing therapeutic potential?

Advanced computational methods offer powerful approaches for predicting immunogenicity and optimizing therapeutic potential:

  • OASis identity scoring: This method effectively differentiates between antibodies of different origins (human, humanized, chimeric, murine) by analyzing 9-mer peptides across prevalence thresholds

  • Transformer-based sequence analysis: Models similar to those used in natural language processing can identify subtle patterns related to immunogenicity

  • Property difference prediction: Sequence-based models like DyAb can predict differences in properties between antibody variants even with limited training data

Research demonstrates these approaches can generate novel antibody variants with enhanced properties using limited training data (~100 labeled sequences) . When implementing these methods:

  • Establish clear immunogenicity criteria based on peptide analysis

  • Balance immunogenicity reduction against binding properties

  • Validate computational predictions with experimental testing

  • Implement iterative optimization cycles

The OASis identity method has been validated on therapeutic antibodies, correctly distinguishing between different origins and identifying outliers with unusual properties , making it particularly valuable for translational MUR4 antibody research.

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