Circulating and storage neutrophils in septic neonatal rats treated with immune globulin.

Marked neutropenia, complete depletion of the neutrophil storage pool, and death within 48 h were observed in newborn rats intrapulmonically inoculated with 10(5) type III group B streptococci (GBS). Intraperitoneal administration of 225 mg of intravenous human immune globulin (IVIG) immediately after intrapulmonic inoculation of GBS significantly lessened the degree of neutropenia and prevented depletion of the neutrophil storage pool and death. No effect of IVIG on neutrophil production was observed in vitro, in cultures of granulocytic progenitor cells, or in vivo, as assessed by quantifying circulating and storage pools in normal neonatal rats injected with IVIG. IVIG, however, markedly hastened release of neutrophils from the reserves into the blood and hastened the arrival of neutrophils at the site of the bacterial injection (the right lung). Specific antibody to GBS, as opposed to a nonspecific IgG effect, appeared to be responsible for the improvements in neutrophils kinetics and for survival of the animals.