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. Author manuscript; available in PMC: 2014 Jul 9.
Published in final edited form as: Nat Rev Immunol. 2013 Feb 8;13(3):190–198. doi: 10.1038/nri3386

Figure 2. Rhythms in immune cell function.

Figure 2

a) Rest-activity cycles in diurnal humans and nocturnal mice. In murine bone marrow and skeletal muscle, leukocyte recruitment is enhanced during the active phase due to higher expression levels of chemokines as well as adhesion molecules on both the endothelium and hematopoietic cells. In peripheral tissues, the molecules oscillating on leukocytes mediating circadian recruitment are not known but likely include CCR2, the receptor for CCL2, and the ICAM-1 binding integrins LFA-1 and Mac-1. During the resting phase, lower adhesion molecule and chemokine expression as well as enhanced mobilization from the bone marrow results in reduced leukocyte recruitment and enhanced numbers of immune cells in blood. b) Oscillation of factors known to contribute to circadian trafficking of hematopoietic cells showing in-phase expression of pro-migratory factors.