Cytokines enhance opsonophagocytosis of type III group B Streptococcus.
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.


OBJECTIVE
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.


METHODS
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.


RESULTS
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.


CONCLUSIONS
G-CSF enhances the neonatal PMN-mediated killing of III GBS in vitro. These studies suggest that use of FcRIII receptors may be one mechanism by which GM-CSF augments the PMN-mediated killing of III GBS. The addition of purified immunoglobulin G containing III GBS-specific antibody facilitated opsonophagocytosis by GM-CSF-treated PMNs. We speculate that the administration of GM-CSF alone or in combination with intravenous immunoglobulin may improve the neonatal host response to III GBS.
Campbell
J R
JR
Department of Pediatrics, Baylor College of Medicine, Houston, TX, USA.
Edwards
M S
MS
D000328:Adult; D004305:Dose-Response Relationship, Drug; D016179:Granulocyte Colony-Stimulating Factor / Q000378:metabolism* / Q000494:pharmacology; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000502:physiology*; D006801:Humans; D066298:In Vitro Techniques; D007231:Infant, Newborn; D009504:Neutrophils / Q000187:drug effects / Q000276:immunology*; D009895:Opsonin Proteins / Q000378:metabolism*; D010587:Phagocytosis / Q000187:drug effects / Q000276:immunology*; D011336:Probability; D012680:Sensitivity and Specificity; D013292:Streptococcus agalactiae / Q000472:pathogenicity*; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*
D009895:Opsonin Proteins; D014409:Tumor Necrosis Factor-alpha; D016179:Granulocyte Colony-Stimulating Factor; D016178:Granulocyte-Macrophage Colony-Stimulating Factor