Abstract
Summary: In an attempt to explain the profound neutropenia and depletion of marrow neutrophil reserves observed in human and experimental group B streptococcal infection, we have studied the stem cell, proliferative, storage, and circulating neutrophil pools in groups of adult and neonatal rats inoculated with 3 × 106 type II group B streptococci/g body weight. At intervals after inoculation, animals were sacrificed and the unipotent granulocytic stem cells, (Colony Forming Units in culture, CFUC) from the femoral marrow were quantified. In addition, the total body neutrophil proliferative pool, neutrophil storage pool, circulating blood neutrophil concentration and blood immature to total neutrophil ratio were measured. Adult animals developed neutrophilia with a peak blood neutrophil concentration of 3.4 times control by 24 h after inoculation (P < 0.001). A left shift was seen in these mature animals as early as 2 h but by 24 h was no longer present. The neutrophil storage pool diminished to 65% of control by 15 h (P < 0.001) but then increased to exceed the control in all animals by 48 h (P < 0.01). The neutrophil proliferative pool did not change during infection in the adult animals, but CFUC increased to three times control 48 h after inoculation (P < 0.001) and returned to baseline by 72 h.
The myeloid response of the neonatal rats was markedly different from that of the adults. Neonates developed profound neutropenia with an extreme left shift, exhaustion of the neutrophil storage pool (less than 10% of control by 15 h, P < 0.001), and diminution of the proliferative pool to 58% of control by 10 h (P < 0.05). In contrast to the adult animals, neonatal rats infected with group B streptococci failed to increase CFUC, and in fact a diminution of CFUC to 48% of control was seen by 15 h (P < 0.05).
Speculation: When adults develop bacterial infection, they often demonstrate neutrophilia and a leukocyte left shift. We observed these findings in infected adult rats accompanied by a moderate, temporary diminution of storage neutrophils and by an elevation in granulocytic stem cells. The adult response enables the animal to deliver large numbers of neutrophils to the infected tissues. In contrast, infected neonates developed profound neutropenia, exhaustion of neutrophil reserves and decreased neutrophii production. The neonatal response results in diminished delivery of neutrophils to infected tissues and a marked increase in mortality. The decreased production of neutrophils accompanying neutrophil storage pool depletion and neutropenia in neonates may constitute a condition for which neutrophil transfusion may represent a reasonable therapeutic approach.
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Christensen, R., Macfarlane, J., Taylor, N. et al. Blood and Marrow Neutrophils during Experimental Group B Streptococcal Infection: Quantification of the Stem Cell, Proliferative, Storage and Circulating Pools. Pediatr Res 16, 549–553 (1982). https://doi.org/10.1203/00006450-198207000-00011
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DOI: https://doi.org/10.1203/00006450-198207000-00011
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