Hematopoietic stem and progenitor cells (HSPC) reside in specific niches in the bone marrow, where they are part of a complex micro-environment. Several cytokines, chemokines and small molecules... Show moreHematopoietic stem and progenitor cells (HSPC) reside in specific niches in the bone marrow, where they are part of a complex micro-environment. Several cytokines, chemokines and small molecules are involved in mobilization of HSPC from the bone marrow towards peripheral blood. This thesis describes several studies on the mechanisms of HSPC mobilization: the kinetics of HSPC mobilization following the administration of Flt3-ligand in a murine model, the effects of repeated in vivo administration of recombinant human G-CSF and murine recombinant G-CSF in mice, the role of alpha-1-antitrypsin in steady state and during G-CSF-induced mobilization in humans and the effects of mesenchymal stromal cells on the stem cell niche in a murine model of G-CSF-induced HSPC mobilization. Show less