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Development and application of a radioimmunoassay to detect interleukin-1 in rat peripheral circulation
1Department of Pharmacology, Medical Faculty, Free University, Amsterdam, The Netherlands.
Insights
A new radioimmunoassay detects interleukin-1 beta (IL-1 beta) in rats. Bacterial lipopolysaccharide (LPS) triggers IL-1 beta release from macrophages, influencing systemic responses.
Area of Science:
- Immunology
- Endocrinology
- Biochemistry
Background:
- Interleukin-1 beta (IL-1 beta) is a key cytokine involved in immune responses.
- Understanding IL-1 beta's role in vivo requires sensitive detection methods.
Purpose of the Study:
- To develop and validate a radioimmunoassay for quantifying circulating IL-1 beta in rats.
- To investigate the release of IL-1 beta in response to bacterial lipopolysaccharide (LPS).
Main Methods:
- Development of a radioimmunoassay for rat IL-1 beta.
- Administration of rat recombinant IL-1 beta (rrIL-1 beta) and LPS to rats.
- Macrophage depletion using liposome-directed suicide.
- Gel filtration of plasma samples.
Main Results:
- The radioimmunoassay detected IL-1 beta in rats treated with rrIL-1 beta or LPS, but not in controls.
- LPS-induced IL-1 beta release was dose- and time-dependent.
- Macrophage depletion abolished the LPS-induced IL-1 beta response.
- Two molecular forms of IL-1 beta were identified in plasma, including a 17-kDa form.
Conclusions:
- IL-1 beta secreted by macrophages acts as a humoral signal molecule.
- This IL-1 beta signaling mediates immunological, metabolic, and neuroendocrine changes following LPS exposure.
Abstract:
We describe the development and application of a radioimmunoassay to detect circulating interleukin (IL)-1 beta concentrations in the rat. No IL-1 immunoreactivity above the detection limit of the assay (100 pg/ml) could be detected in plasma of control rats. In contrast, immunoreactive IL-1 was detected after intravenous administration of rat recombinant IL-1 beta (rrIL-1 beta) or bacterial lipopolysaccharide (LPS) to rats. The effect of LPS on plasma immunoreactive IL-1 concentrations was time and dose dependent. The immunoreactive IL-1 response to LPS was prevented by in vivo macrophage depletion induced by liposome-directed macrophage suicide technique. Gel filtration of plasma from LPS-treated rats revealed the presence of a high and a smaller molecular form of immunoreactive IL-1. The small molecular immunoreactive IL-1 peak coeluted with rrIL-1 beta and probably represents the 17-kDa form of IL-1 beta. In conclusion, our data support the hypothesis that IL-1 secreted by macrophages can act as a humoral signal molecule to induce the immunological, metabolic, and neuroendocrine changes in response to bacterial LPS.