Within the bone marrow microenvironment, dynamic cellular interactions
are constantly occurring. These interactions involve hemopoietic stem
cells, progenitor cells and maturing cells, physically interacting wi
th other cells, some of which may function as accessory cells, and oth
ers which comprise the stromal elements; hemopoietic cells also intera
ct with non-cellular elements, such as glycoproteins and fibrous prote
ins of the extracellular matrix (ECM). These interactions serve to reg
ulate normal hemopoiesis by allowing the communication of regulatory i
nformation, migration and subsequent homing of stem cells within speci
fic organs, and presentation of hemopoietic growth factors in a biolog
ically relevant fashion. The goal of this review is to examine the spe
cific cellular interactions that relate to the phenomenon of homing of
intravenously transplanted stem cells to the bone marrow.