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Radioimmunoassay of interleukin-6 in plasma
A M Teppo1, K Metsärinne, F Fyhrquist
1IV Department of Medicine, Helsinki University Central Hospital, Finland.
Insights
We developed a radioimmunoassay to measure human interleukin-6 (IL-6) in biological fluids. This assay detected elevated IL-6 levels in patients with multiple myeloma, rheumatoid arthritis, and severe infections.
Area of Science:
- Immunology
- Biochemistry
- Clinical Chemistry
Background:
- Interleukin-6 (IL-6) is a key cytokine involved in immune responses and inflammation.
- Accurate quantification of IL-6 in biological fluids is crucial for understanding various disease states.
Purpose of the Study:
- To develop and validate a sensitive double-antibody radioimmunoassay for human IL-6.
- To determine normal and elevated IL-6 concentrations in different patient populations.
Main Methods:
- Double-antibody radioimmunoassay technique.
- Measurement of IL-6 in serum and plasma samples.
- Analysis of samples from healthy subjects and patients with specific diseases.
Main Results:
- The assay has a detection limit of 20 ng/L and a dynamic range of 100-14,000 ng/L.
- Plasma IL-6 levels were approximately 85 ng/L higher than serum levels.
- Elevated IL-6 was observed in multiple myeloma (303 ng/L), rheumatoid arthritis (234 ng/L), and systemic lupus erythematosus (183 ng/L).
- Markedly increased IL-6 (>3000 ng/L) was found in meningococcus meningitis and infectious peritonitis.
Conclusions:
- The developed radioimmunoassay is suitable for quantifying human IL-6 in biological samples.
- IL-6 levels are significantly elevated in several inflammatory and infectious conditions.
- This assay can aid in the diagnosis and monitoring of diseases associated with IL-6 dysregulation.
Abstract:
We present a double-antibody radioimmunoassay for determining human interleukin-6 (IL-6) in biological fluids. The detection limit of the assay is 20 ng/L (B0 - 2 SD). Bound radioactivity in the range of 30% to 90% of the B0 counts corresponds to IL-6 concentrations of 100 to 14,000 ng/L. Analytical recovery of IL-6 added to EDTA-treated plasma averaged 25% more than that added to serum. The plasma concentration of IL-6 was therefore approximately 85 ng/L more than the concentration in simultaneously drawn serum. The mean serum concentration of IL-6 in 45 healthy subjects was 83 ng/L (range 20-290 ng/L), in 20 patients with multiple myeloma 303 ng/L, in 20 patients with rheumatoid arthritis 234 ng/L, and in 13 patients with systemic lupus erythematosus 183 ng/L. Markedly increased (greater than 3000 ng/L) concentrations of IL-6 were found in sera of patients with meningococcus meningitis and infectious peritonitis.