The present disclosure generally teaches compositions comprising SDF-1 mimetics and methods of using them to modulate an activity of a cell having an SDF-1 receptor by binding the SDF-1 receptor to an SDF-1 mimetic. The cell can be a hematopoietic cell, for example, and can be selected from a group consisting of hematopoietic stem cells, hematopoietic progenitor cells, primitive granulocytes, primitive erythroid cells, leukocytes, and neutrophils. In some embodiments, the activity can include the rate of multiplication of the cell or, where the cell is a quiescent cell, the binding can repress the activation of the quiescent cell. Other embodiments of the present invention are taught herein.