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Studies on the release of cell-associated interleukin 1 by paraformaldehyde-treated murine macrophages
H Streck1, C Günther, H U Beuscher
1Institut für Klinische Mikrobiologie der, Friedrich-Alexander-Universität, Erlangen-Nürnberg, FRG.
Abstract:
Experiments are presented demonstrating the release of interleukin 1 (IL1) by lipopolysaccharide-stimulated murine macrophages (M phi) after treatment of the cells with paraformaldehyde (PFA). The IL1 activity set free was completely blocked by a rabbit anti-mouse IL1 alpha antiserum. Immunoprecipitation studies revealed that the IL1 released was of Mr 33 kDa, 23 kDa and 17 kDa. Incubation of PFA-treated M phi in the presence of leupeptin reduced the amount of detectable low molecular mass (i.e. 23 kDa and 17 kDa) IL1 alpha. Addition of leupeptin to PFA-treated M phi also reduced the amount of released IL1 activity, suggesting that proteolytic modification of the IL1 alpha precursor is involved in the generation of biological active IL1 alpha. It is proposed that the cell-associated 33-kDa IL1 is released from the M phi by vesiculation of parts of the M phi cell membrane, followed by a proteolytic cleavage step.
Insights
Paraformaldehyde treatment releases interleukin 1 (IL1) from macrophages. Proteolytic cleavage of IL1 alpha is involved in generating biologically active IL1, suggesting a vesiculation and shedding mechanism.
Area of Science:
- Immunology
- Cell Biology
Background:
- Interleukin 1 (IL1) is a key cytokine involved in inflammatory responses.
- Macrophages (M phi) are critical immune cells that produce and release IL1.
Purpose of the Study:
- To investigate the mechanism of IL1 release from lipopolysaccharide-stimulated murine macrophages after paraformaldehyde (PFA) treatment.
- To identify the molecular weight of released IL1 and the role of proteolytic processing.
Main Methods:
- Stimulation of murine macrophages with lipopolysaccharide (LPS).
- Treatment of macrophages with paraformaldehyde (PFA).
- Detection of IL1 activity using IL1 alpha antiserum and immunoprecipitation.
- Analysis of IL1 molecular weight and the effect of leupeptin.
Main Results:
- PFA treatment induced the release of IL1 activity from macrophages.
- Released IL1 was detected at molecular weights of 33 kDa, 23 kDa, and 17 kDa.
- Leupeptin treatment reduced the levels of lower molecular mass IL1 (23 kDa and 17 kDa) and overall IL1 activity, indicating proteolytic processing.
Conclusions:
- The release of IL1 from PFA-treated macrophages involves proteolytic modification of IL1 alpha.
- A proposed mechanism involves vesiculation of the macrophage cell membrane releasing cell-associated 33-kDa IL1, followed by proteolytic cleavage to generate active IL1 alpha.