Circadian regulation of neutrophils: Control by a cell-autonomous clock or systemic factors?

In the first section of this review we present the recent model of the mammalian molecular clock by introducing the main transcription-translation feedback loops and discussing the pace-setting role of post-translational modifications. The next sections summarize clinical, epidemiological and experimental data regarding the daily control of immune responses and studies analysing expression of clock components in various leukocytes and particularly, in human peripheral neutrophils. As the latter data indicate that expression of components of the cell-autonomous clock is relatively low in neutrophils, in the last section we review recent findings suggesting a role for systemic and local factors in the regulation of rhythmic neutrophil responses.