In vivo study of lactoferrin and murine rebound myelopoiesis

Lactoferrin has been reported to inhibit the production of colony-stimulating factor (CSF); thus we sought to study its possible effects on myelopoiesis in vivo. The characteristics of rebound myelopoiesis in C57BL mice injected with a sublethal dose of cyclophosphamide (CY) were used to test lactoferrin for any granulopoietic activity. An experimental group received daily injections of 50 micrograms of human lactoferrin beginning 24 hr after CY injections. By measuring the total nucleated cellularity of the femoral marrow, the peripheral blood count, and the incorporation of tritiated thymidine by the marrow in six replicate experiments, no statistically significant difference was noted between the lactoferrin injected groups and the control groups. Neither the route of lactoferrin administration (i.v. or i.p.) nor the sex of the animal altered the myelopoietic recovery. Lactoferrin had no stimulatory or inhibitory effect on murine rebound myelopoiesis in vivo contrary to the reported in vitro results.