Pre- and Postnatal Development of Granulocytic Stem Cells in the Rat

Neutrophil Pool Sizes and Granulocyte Colony-Stimulating Factor Production in Human Mid-Trimester Fetuses

“…Mononuclear cells from the fetal bone marrow produced less G-CSF protein and mRNA than did mononuclear cells from the blood of The NSP is the sum of all segmented neutrophils, band neutrophils, and metamyelocytes held in reserve for ready release into the circulation (1). Rat pups delivered prematurely have a much smaller NSP, per g of body weight, than do those delivered at term, and pups delivered at term have a smaller NSP than do adult rats (2)(3)(4)(5)(6). It is unknown, however, whether this observation applies to humans.…”

“…For instance, in a previous study we observed that newborn rats had only 25% of the NSP, per g body weight, of adult rats (2). We also observed that the quantity of CFU-GM per g body weight in newborn rats was only about 10% that of adult rats (4). In this study, granulocytic progenitors were indeed present in human fetal liver and marrow, excluding the hypothesis that the lack of granulocytopoiesis in the fetal liver was the result of lack of CFU-GM in that organ.…”

Neutrophil Production and Function in Newborn Infants

“…These have shown that newborn rats have a total pool of GM-CFU that is less than 10% of the GM-CFU per gram body weight of adults and unlike adults, who have a large pool of quiescent progenitors to recruit into the cell cycle in the face of sepsis, over 75% of GM-CFU in noninfected newborn rats are in active cell cycle (Christensen et al, 1984;Christensen, 1988). Circumstantial evidence for a similar immaturity of granulopoiesis in human neonates comes from studies in infants born at or near term which show a similar pattern of continuous near maximal GM-CFU proliferation (Christensen et al, 1986) compared with the large reserve of non-proliferating GM-CFU in human adults (Fauser & Messner, 1979).…”

Decreased Stimulated GM-CSF Production and GM-CSF Gene Expression but Normal Numbers of GM-CSF Receptors in Human Term Newborns Compared with Adults

“…Specific differences in myelopoiesis have been demonstrated in term newborn rats compared with adult animals. Reduced neonatal rat myeloid progenitor pools, accelerated myeloid progenitor proliferative rates, and decreased total body neutrophil storage pools all predispose the newborn rat to depletion of mature effector neutrophils and a tendency to develop neutropenia during states of increased demand or overwhelming bacterial sepsis (2)(3)(4). During experimental sepsis (states of increased demand), adult animals increase their CFU-GM pool two to three times greater than baseline and increase their proliferative rate to approximately 75% of maximal capacity.…”