['Neutrophil (polymorphonuclear leukocyte (PMN)-mediated killing is important to host defense against type III group B Streptococcus (GBS). In neonates, a qualitative and quantitative deficiency in PMN-mediated host defense may contribute to an impaired neonatal response to this pathogen.', 'The purpose of this study was to determine whether tumor necrosis factor-alpha (TNF-alpha), granulocyte colony-stimulating factor (G-CSF), or granulocyte-macrophage colony-stimulating factor (GM-CSF) would enhance neonatal PMN-mediated killing of III GBS.', 'PMNs from adults or neonates were incubated with TNF-alpha, G-CSF, or GM-CSF; next, PMN-mediated killing of III GBS was assessed in an in vitro opsonophagocytic assay.', 'Treatment of PMNs with these cytokines for an interval of 5 minutes before addition of GBS to the reaction mixture enhanced opsonophagocytosis of bacteria both by adult PMNs and neonatal PMNs. The effect was statistically significant for TNF-alpha- and GM-CSF-treated adult PMNs and for GM-CSF-treated neonatal PMNs. The enhanced killing of III GBS by GM-CSF-treated PMNs was reduced by monoclonal antibody blockade of FcRIII.'] Do cytokines enhance opsonophagocytosis of type III group B Streptococcus?