Immunoradiometric assay for human complement component C9 utilising monoclonal antibodies.

Area of Science:

• Immunology
• Biochemistry
• Clinical Chemistry

Background:

• The complement system plays a crucial role in immune responses.
• Human complement component 9 (C9) is the terminal component of the complement cascade.
• Accurate measurement of C9 is important for understanding its role in various diseases.

Purpose of the Study:

• To develop and validate a novel, highly sensitive two-site immunoradiometric assay for human C9.
• To quantify C9 concentrations in normal human plasma.
• To investigate C9 levels in plasma from patients with rheumatoid arthritis and in cerebrospinal fluid.

Main Methods:

• Development of a two-site immunoradiometric assay using two non-competing monoclonal antibodies against C9.
• Single incubation assay protocol for C9 detection.
• Measurement of C9 concentrations in human plasma, cerebrospinal fluid, and synovial fluid.

Main Results:

• The assay demonstrated a detection limit of 0.1 ng in 100 microliters, with high sensitivity.
• Normal human plasma C9 concentration was determined to be 60.2 +/- 14.9 mg/l.
• Significantly elevated C9 levels (90.4 +/- 19.9 mg/l) were observed in rheumatoid arthritis patients.
• Low levels of C9 in cerebrospinal fluid (<1 mg/l), previously undetectable, were easily measured.

Conclusions:

• The developed immunoradiometric assay is highly sensitive and specific for human C9.
• The assay allows for the detection of elevated C9 in rheumatoid arthritis and low C9 levels in cerebrospinal fluid.
• This assay provides a valuable tool for research into the role of C9 in health and disease.