Immunoglobulin isotype identification in red cell antibodies using flow cytometry

Area of Science:

• Immunology
• Clinical Chemistry
• Flow Cytometry

Background:

• Accurate immunoglobulin (Ig) isotype identification (IgM vs. IgG) is critical for predicting hemolytic disease of the newborn.
• Current 2-mercaptoethanol (2-ME) treatment for IgM degradation has significant drawbacks.
• A need exists for a more efficient and reliable method for Ig isotype differentiation.

Purpose of the Study:

• To develop and validate a flow cytometry (FC) assay to replace the conventional 2-ME treatment protocol.
• To establish a superior method for distinguishing between IgM and IgG in patient samples.

Main Methods:

• Development and refinement of a preliminary FC assay using stock antibodies.
• Parallel testing of 10 antibody-containing samples using both the FC assay and 2-ME treatment.
• Utilized a 10-unit mean channel fluorescence change as a positive result index.

Main Results:

• The FC assay demonstrated equivalent accuracy to 2-ME treatment in differentiating IgG from IgM.
• The FC assay successfully identified all isotypes detected by 2-ME treatment, including mixtures.
• The FC assay detected an antibody missed by conventional agglutination testing, highlighting potential IgA presence.

Conclusions:

• The developed FC assay is a viable and accurate alternative to 2-ME treatment for Ig isotype differentiation.
• The FC assay offers advantages including positive endpoint detection for both isotypes, IgA identification, reduced sample requirement, and absence of odor.
• This FC assay provides a more efficient and sensitive method for clinical diagnostics.