SP-D Immunoassay Using One Monoclonal Antibody Across Multimers

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Solution Overview

Problem

Conventional methods for measuring pulmonary surfactant protein D (SP-D) face challenges due to variations in multimer distribution, leading to fluctuations in reactivity and quantification accuracy due to changes in the number of monomers constituting the multimer, such as from a dodecamer to a 36-mer.

Innovation Solution

A method involving a sample contact with an insoluble carrier immobilized with a single type of anti-SP-D monoclonal antibody, allowing detection of SP-D multimers by forming complexes with labeled antibodies, specifically targeting trimers and larger multimers.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If conventional sandwich ELISA methods are used to measure SP-D, then the measurement can be conducted using two types of antibodies, but variations in multimer distribution cause fluctuations in reactivity and quantification accuracy

Engineering Contradiction:
Improvequantification accuracyVSAvoidreactivity consistency
Core Design Contradiction:
Measurement precisionVSReliability

Solution Approach 1:

The patent applies homogeneity by using only one type of monoclonal antibody for both capturing and detecting SP-D multimers. This ensures uniform recognition of the same epitope across all multimer sizes (trimers, dodecamers, 36-mers), eliminating the reactivity variations that occur when different antibodies with different specificities are used. The homogeneous antibody approach ensures consistent quantification regardless of multimer distribution variations.

Inventive Principle:
Principle #33Homogeneity

2Adaptability or versatility

If multiple types of antibodies are used in sandwich ELISA, then detection capability is enhanced, but differences in multimer distribution result in changes in SP-D quantitative values

Engineering Contradiction:
Improvedetection capabilityVSAvoidquantitative value consistency
Core Design Contradiction:
Adaptability or versatilityVSMeasurement precision

Solution Approach 1:

The patent extracts and eliminates the source of measurement error by removing the second antibody from the sandwich ELISA system. Instead of using two different antibodies that may recognize different epitopes with varying affinities across multimer sizes, the invention uses a single monoclonal antibody for both capture and detection functions, thereby eliminating the variability introduced by antibody heterogeneity.

Inventive Principle:
Principle #2Taking out (Extraction)

Solution Approach 2:

The single monoclonal antibody is designed to perform multiple functions: it serves as both the capture antibody immobilized on the solid phase and the detection antibody in solution. This universal antibody approach ensures consistent recognition of SP-D multimers across different multimer sizes, achieving both detection capability and quantitative precision.

Inventive Principle:
Principle #6Universality (Multi-functionality)

3Adaptability or versatility

If the number of monomers in SP-D multimer changes (e.g., from dodecamer to 36-mer), then the biological function may vary, but epitope concentration changes cause fluctuations in antibody reactivity

Engineering Contradiction:
Improvemultimer size variationVSAvoidavidity consistency
Core Design Contradiction:
Adaptability or versatilityVSReliability

Solution Approach 1:

The patent addresses the issue of changing physical parameters (multimer size, epitope concentration, avidity) by using a monoclonal antibody that recognizes a conserved epitope structure present across all multimer sizes. This approach transforms the measurement system's insensitivity to parameter changes into a strength, allowing reliable quantification regardless of whether the SP-D exists as trimers, dodecamers, or 36-mers.

Inventive Principle:
Principle #35Parameter changes

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

Enables accurate quantification of SP-D regardless of the number of monomers in the multimer, ensuring precise measurement results.

Implementation Method 1

a step of bringing a sample containing pulmonary surfactant protein D into contact with an insoluble carrier on which an anti-pulmonary surfactant protein D monoclonal antibody has been immobilized, and a step of detecting a complex of the pulmonary surfactant protein D and at least two of the anti-pulmonary surfactant protein D monoclonal antibodies

Methodology Applied
Scientific EffectAntigen-antibody binding:

Implementation Method 2

an insoluble carrier on which an anti-pulmonary surfactant protein D monoclonal antibody has been immobilized

Methodology Applied
Scientific EffectImmobilization: Adsorption

Data Source

PatentEP4685487A1Method for measuring pulmonary surfactant protein d, measurement kit, monoclonal antibody, and cell
Publication Date: 2026.01.28 SEKISUI MEDICAL CO LTD
  • EP4685487A1 patent drawingFigure 1(a)~1(h)
  • EP4685487A1 patent drawingFigure 2
  • EP4685487A1 patent drawingFigure 3

AI summary

This method for measuring pulmonary surfactant protein D includes a step of bringing a sample containing pulmonary surfactant protein D into contact with an insoluble carrier on which an anti-pulmonary surfactant protein D monoclonal antibody has been immobilized, and a step of detecting a complex of the pulmonary surfactant protein D and at least two of the anti-pulmonary surfactant protein D monoclonal antibodies, wherein the insoluble carrier supports only one type of antibody as the anti-pulmonary surfactant protein D monoclonal antibody.