THE FAILURE OF NEWBORN MICE INFECTED WITH ESCHERICHIA-COLI TO ACCELERATE NEUTROPHIL PRODUCTION CORRELATES WITH THEIR FAILURE TO INCREASE TRANSCRIPTS FOR GRANULOCYTE-COLONY-STIMULATING FACTOR AND INTERLEUKIN-6

We quantified circulating and storage neutrophils, their precursors an d progenitors, and mRNA for some of the cytokines involved in granuloc ytopoiesis, in newborn and adult mice following intrapulmonary inocula tion of Escherichia coli. Four hours following inoculation of adult an d newborn mice with a quantity of organisms 2 logs below the LD(100), all animals were neutropenic. After 24 h, adults had recovered from th e neutropenia but neonates had not (p < 0.001). Accelerated neutrophil production was evident in the infected adults, and correlated with th e appearance of granulocyte colony-stimulating factor (G-CSF) transcri pts in the liver, spleen, and lung, and interleukin-6 (IL-6) transcrip ts in the spleen and lung. An increase in neutrophil production was no t observed in the neonates, and none of their organs tested had transc ripts for either G-CSF or IL-6, but they did have transcripts for cyto kines not involved in granulocytopoiesis; macrophage colony-stimulatin g factor and its receptor (c-fms). We speculate that the failure to in crease neutrophil production in infected neonatal mice is the result o f failure to increase production of relevant cytokines.