Different cytokine expression in cord blood mononuclear cells after stimulation with neonatal sepsis or colonizing strains of Streptococcus agalactiae

Streptococcus agalactiae (group B streptococcus, GBS) is the major pathogen of neonatal sepsis. in some newborns, GBS sepsis may have a severe course, including septic shock with a high mortality rate, whereas other newborns are colonized with GBS on their surfaces without any clinical signs of bact erial infection. The reason for this discrepancy is far from clear. We soug ht, in this study, to compare cytokine expression in cord blood mononuclear cells after stimulation with GBS strains isolated from newborns with sepsi s, and strains isolated from newborns without any symptoms of invasive infe ction. Cord blood mononuclear cells were incubated with either heat-killed bacteria of different strains or lipopolysaccharide, respectively. After 6 and 24 h, cells were harvested and cytokine mRNA-expression was analyzed by reverse-transcriptase PCR. Likewise, supernatants were tested for IL-6 and tumor necrosis factor-alpha concentrations by enzyme immunoassay. When com paring IL-6 and tumor necrosis factor-alpha secretion, there were significa ntly higher IL-6 levels after stimulation with sepsis than with colonizing isolates. Likewise, mRNA expression of IL-6, IL-1 beta, and IL-12p40 was si gnificantly higher after stimulation with sepsis isolates. This was also tr ue when normalizing to cytokine expression after stimulation with lipopolys accharide. These findings indicate that the different clinical pictures in response to GBS, either septic infection or colonization. might reflect str ain-specific properties. If the respective characteristics can be defined, it might become possible to distinguish by molecular methods potentially "d angerous" from "harmless" strains. Moreover, our findings underline the ess ential role of these cytokines in the pathogenesis of neonatal GBS sepsis.