Further studies on the mechanism of marrow granulocytic hyperplasia in mice chronically injected with endotoxin

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Abstract
Marrow granulocytic hyperplasia occurs regularly in mice injected with endotoxin for 7‐30 d, despite minimal elevations of serum colony‐stimulating activity (CSA). Alterations in marrow granulocyte‐monocyte progenitor (CFU‐C) number or changes in marrow cell cycle status do not explain this hyperplasia. We have studied other mechanisms which may explain this increased granulopoiesis. CF1, BDF1 or C57bl/6J mice were injected with 10 μg of S. typhosa, endotoxin i.p. daily for 7‐20 d. Control and endotoxin injected (tolerant) sera, each with identical levels of CSA, were assayed against control marrow cells stimulated with supramaximal amounts of CSA to assess the role of serum potentiators in augmenting granulopoiesis. In six separate experiments, tolerant sera, over a 30‐fold concentration range, produced a 1.7–4.0‐fold potentiation of colony growth compared to control sera (Pin vitro, may reflect prior in vivo, exposure of marrow to these potentiating factor(s).