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Circulating cytokines: the tip of the iceberg?
J M Cavaillon1, C Munoz, C Fitting
1Unité d'Immuno-Allergie, Institut Pasteur, Paris, France.
Insights
Circulating cytokines like TNF alpha are key during severe infections. Their presence in blood is complex, often indicating more extensive cytokine activity than detectable levels suggest, representing just the "tip of the iceberg."
Area of Science:
- Immunology
- Biochemistry
Background:
- Severe infections trigger activated cells to release cytokines, including TNF alpha, IL-1, IL-6, and IL-8.
- The levels of circulating cytokines are influenced by a complex interplay of production, degradation, cell signaling, and receptor modulation.
Purpose of the Study:
- To explore the complex dynamics of cytokine presence and activity in biological fluids during severe infections.
- To discuss the concept that detectable circulating cytokines represent only a fraction of the overall cytokine-mediated response.
Main Methods:
- Review and discussion of existing literature on cytokine detection and activity.
- Analysis of the balance between cytokine production, inhibition, catabolism, and receptor interactions.
Main Results:
- Detectable circulating cytokines, such as TNF alpha, do not always correlate with their biological activity.
- The absence of detectable cytokines in circulation does not preclude their active production by cells.
Conclusions:
- Circulating cytokine levels are a simplified indicator of a more intricate biological process.
- The concept of circulating cytokines as the "tip of the iceberg" highlights the need for a comprehensive understanding of cytokine networks in disease.
Abstract:
Circulating cytokines, particularly TNF alpha, IL-1, IL-6 and IL-8, can be detected during severe infections consecutively to an exacerbate release by activated cells. The presence or absence of cytokines within biological fluids reflects a rather complex balance between enhancing and inhibitory signals acting on producer cells, between production and catabolism, and between their binding to the target cells and the modulation of their receptors on the cell surface. Furthermore, their presence does not necessarily parallel their activity and a possible interplay between the cytokines and their corresponding inhibitors should be considered. On the contrary, the absence of detectable circulating cytokines does not indicate an absence of production by activated cells. We discuss the concept that circulating cytokines represent the tip of the iceberg.