The absolute quantification of human IgM and IgG: standardization and normal values.

Area of Science:

• Immunology
• Biochemistry
• Clinical Chemistry

Background:

• Accurate quantification of immunoglobulins is crucial for diagnosing and monitoring various diseases.
• Existing methods for determining immunoglobulin levels may have limitations in reproducibility and standardization.
• The International Unit (IU) is a standard measure, but its consistency for specific proteins like IgM and IgG requires evaluation.

Purpose of the Study:

• To describe and validate nephelometric, turbidimetric, and radial immunodiffusion methods for quantifying human IgM and IgG by weight.
• To assess the interference of IgM subgroups and IgG subclasses on these measurement methods.
• To evaluate the consistency of the International Unit (IU) for human IgM and IgG and propose recommendations.

Main Methods:

• Nephelometry, turbidimetry, and radial immunodiffusion techniques were employed for quantitative analysis.
• Human serum samples were analyzed to determine the weight of IgM and IgG.
• Interference from IgM subgroups (7S-IgM) and IgG subclasses was investigated.

Main Results:

• The described methods provide valid and reproducible determination of human IgM and IgG by weight.
• IgM subgroups and IgG subclasses did not interfere with the applied measurement techniques.
• The International Unit for IgG was found to be a constant weight quantity, aligning with WHO estimations.
• The International Unit for IgM was not constant, yielding significantly lower values, leading to a suggestion for its abolition.

Conclusions:

• Nephelometric, turbidimetric, and radial immunodiffusion are reliable methods for quantifying human IgM and IgG.
• The International Unit is inconsistent for human IgM and should be abolished.
• Significant variations in absolute IgM levels were observed based on sex and age (5-80 years).