Figure 1.

The homing code and the mechanisms for regulating tissue- and leukocyte-specific homing. (A) Distinct leukocyte subsets recruited rhythmically (more in the evening) to different organs based on the tissue- and leukocyte- specific oscillatory expression (red dots) of pro-migratory molecules. Targeting different pro-migratory molecules can decrease (green square) or increase (orange square) the homing of specific leukocyte subsets, depending on the cell type as well as homing location. Modified, with permission, from He et al. (3). (B) The circadian system regulates the oscillatory expression of pro-migratory molecules through the systemic circadian signals as well as the cell-intrinsic molecular clock.