Like many aspects of physiology, functions of the immune system show considerable diurnal variation. Studies investigating diurnal variations in the circulating amounts of cytokines, in general, used blood samples obtained from an intravenous catheter. The results of such studies may be confounded by an effect of the catheter on local cytokine production. We measured the levels of IL-6, tumour necrosis factor α (TNF-α) and soluble TNF receptors (sTNIF-R) p55 and p75 in 20 healthy men between 09:00 and 19:00 h in plasma samples obtained from an intravenous catheter and in one additional sample obtained by a simple needle stick in the contralateral arm 10 h after baseline. In plasma from the catheter the levels of IL-6 increased significantly over time, TNF-α levels slightly decreased and the time courses of TNF receptor levels showed significant trends of a higher order. Control levels of IL-6, TNF-α and sTNF-R p75 measured in plasma obtained by needle stick after 10 h did not differ from baseline, and those of sTNF-R p55 were even higher. We conclude that local alterations in the production of cytokines and soluble cytokine receptors induced by an intravenous catheter represent an important confounding factor for studies investigating diurnal variations in immune functions. (C) 2000 Academic Press.
Bibliographical noteFunding Information:
We thank Ms Irene Gunst and Ms Gabriele Kohl for excellent technical assistance. This study was supported by a grant from the German Israel Foundation.
- Diurnal variations
- Intravenous catheter
- Soluble TNF receptors