A sandwich ELISA for properdin in clinical specimens

Area of Science:

• Immunology
• Biochemistry
• Clinical Chemistry

Background:

• Properdin (P) is a key complement system protein.
• Accurate measurement of properdin in serum is crucial for diagnosing complement-related disorders.
• Existing assays may have limitations in sensitivity or specificity.

Purpose of the Study:

• To develop and validate a symmetrical sandwich ELISA for quantifying human properdin (P) in serum.
• To establish a reliable and reproducible method for properdin measurement.

Main Methods:

• Developed a sandwich ELISA using a commercial antiserum globulin fraction as the capture antibody.
• Utilized an alkaline phosphatase conjugate of the Ig fraction as the detecting reagent.
• Analyzed serum samples and purified properdin, fitting data to a quadratic equation in log-log mode.

Main Results:

• The assay detected purified properdin down to 10 ng/ml.
• Established a standard curve where 1 ELISA unit (EU) equals 0.57 microgram of properdin.
• Demonstrated high recovery rates (96-117%) in spiked serum samples.
• Showed low day-to-day variation for normal human sera (mean difference -0.85 EU/ml).

Conclusions:

• The developed sandwich ELISA is an adequate immunochemical assay for human properdin in serum specimens.
• The assay is sensitive, reproducible, and suitable for clinical diagnostic applications.
• Properdin levels in normal human serum were quantified using ELISA units (EU/ml).