Low avidity as a cause of prozone phenomena

Area of Science:

• Immunology
• Immunoassays
• Biochemistry

Background:

• Prozones, or false-negative zones, can occur in immunoassays.
• Understanding prozone formation is crucial for accurate diagnostic testing.
• Anti-immunoglobulin (anti-Ig) reagents are commonly used in various immunoassays.

Purpose of the Study:

• To investigate the factors contributing to prozone formation in immunoassays.
• To elucidate the role of antibody avidity in prozone phenomena.
• To analyze the interaction between low and high avidity antibodies and anti-Ig.

Main Methods:

• Studied prozone incidence in a model indirect haemagglutination system.
• Utilized radioimmunoassay (RIA) to examine prozone formation.
• Employed anti-immunoglobulin (anti-Ig) reagents in both assay systems.

Main Results:

• Prozone formation was correlated with the presence of low avidity antibodies.
• Low avidity antibodies competed with high avidity antibodies for limited anti-Ig.
• Immune aggregates formed by low avidity antibodies and anti-Ig were susceptible to washing off.

Conclusions:

• Low avidity antibodies can occupy anti-Ig without effectively participating in the assay.
• This competition can lead to reduced haemagglutination or radioimmunoassay signal.
• Antibody avidity is a critical factor influencing prozone phenomena in anti-Ig based assays.