Circadian variations do not have a major impact on serum levels of soluble (S) L-selectin (CD63L), S-intercellular adhesion molecule 1 (sICAM-1/CD54) and thrombopoietin in healthy individuals.

The systemic levels of many soluble adhesion molecules and cytokines are altered in hematologic malignancies, autoimmune diseases and serious infections. Among mediators that show altered serum levels are soluble (S) L-selectin (CD63L) and soluble intercellular adhesion molecule-1 (ICAM-1/CD54) expressed by immunocompetent and hematopoietic cells and the hematopoietic growth factor thrombopoietin (Tpo). In the present study, we investigated whether the serum levels of these mediators show circadian variations in healthy individuals. Venous blood serum levels of all three mediators showed only minimal variations when measured regularly during a 24-h period. In contrast, previous studies have demonstrated that the systemic levels of these mediators are markedly altered during serious bacterial infection (SL-selectin, sICAM-1) and severe thrombocytopenia (Tpo). The results suggest that serum sampling at standardized times is probably not required in the future clinical evaluation of these three parameters. [ABSTRACT FROM AUTHOR]