Timothy R. La Pine

Effects of Group B Streptococci on Cord and Adult Mononuclear Cell Interleukin-12 and Interferon-γ mRNA Accumulation and Protein Secretion

Group B streptococci (GBS) are a major cause of early-onset infection in neonates. Neonates, who have defects in neutrophil function that likely contribute to susceptibility to GBS infection, are deficient in the production of the phagocyte activator interferon (IFN)-gamma. GBS-stimulated mRNA accumulation and protein secretion of IFN-gamma and interleukin (IL)-12, a major enhancer of IFN-gamma production, by mixed mononuclear cells (MMCs) from umbilical cord and adult peripheral blood was examined. GBS-exposed cord blood MMCs secreted lower concentrations of both IL-12 and IFN-gamma proteins than did MMCs from adults. IL-12 and IFN-gamma mRNA accumulation was examined by use of comparative reverse transcriptase-polymerase chain reaction. Cord blood MMCs accumulated less mRNA for both IL-12 and IFN-gamma than did adult blood MMC. The deficiency in cord blood cell production of IL-12 may have a role in inadequate IFN-gamma production, which contributes to the unique susceptibility of neonates to GBS infections.

Multiplex analysis of toll-like receptor-stimulated neonatal cytokine response.

Background: The human neonate’s increased susceptibility to bacterial infections is not completely understood. Toll-like receptors (TLRs) have been recognized as pattern-recognition receptors critical to the innate immune response. TLR function in neonates, however, remains incompletely defined. Objective: To examine regulatory and proinflammatory cytokine responses to TLR-1–6 stimulation of cord blood compared to adult blood. Methods: We stimulated cord blood with ligands for each of TLRs 1–6 and compared these responses to adult controls. The following TLR ligands were utilized: Pam3CSK4 (TLR-1 and 2), zymosan (TLR-2 and 6), poly I:C (TLR-3), LPS (TLR-4), and flagellin (TLR-5). Cytokine production was measured with an assay developed in-house utilizing multi-analyte technology. Results: TLR-1–6 stimulation produced higher concentrations of proinflammatory cytokines (IL-1β, IL-6, and IL-8) in cord blood compared to adult blood, with the exception of TLR-4-stimulated TNF-α production, which was significantly lower in cord blood (319 pg/ml) compared to adult blood (645 pg/ml; p = 0.027). In contrast, TLR-1–6 stimulation resulted in decreased concentrations of Th1 and Th2 cytokines in cord blood compared to adult blood, with significantly diminished production of IL-12 (TLRs 1/2, 2/6, 3 and 4), IL-13 (TLR-1–6), and IL-10 (TLR-4). Conclusion: Cord blood production of regulatory Th1 and Th2 cytokines following TLR stimulation is decreased compared to that of adult blood. In contrast, TLR-stimulated proinflammatory cytokine production was markedly higher in neonates than in adults, with the exception of TLR-4-induced TNF-α production. The human neonate’s increased susceptibility to bacterial infections may be related to abnormal TLR responsiveness, with enhanced proinflammatory and decreased regulatory cytokine production.

Effects of Group B Streptococci on Cord and Adult Mononuclear Cell Transcription and Translation of IL-12 and IFN-gamma

Effects of Group B Streptococci on Cord and Adult Mononuclear Cell Transcription and Translation of IL-12 and IFN-gamma

Severely depressed interleukin-17 production by human neonatal mononuclear cells

Background:The role of T-helper 17 cells (Th17) in neonatal host defense remains to be fully elucidated. Interleukin (IL)-17 plays an important role in the immune response to bacterial and fungal pathogens by promoting inflammation.Methods:We examined neonatal production of IL-17 in mixed mononuclear cells (MMCs) isolated from umbilical cord blood for comparison with adult peripheral blood mononuclear cell controls.Results:IL-17 production was profoundly diminished in MMCs isolated from cord blood when compared with MMCs from adult blood. This was associated with a marked reduction in the population of CCR6+ IL-17+ T-cells in the neonatal cord blood. We also found diminished intracellular formation of IL-17, and diminished IL-17 responses to both group B streptococci (GBS) and Escherichia coli. Neonatal mononuclear cells were found to adequately phosphorylate signal transducer and activator of transcription 3, pY705, and pS727. We and others have reported markedly reduced interferon-γ production by neonate mononuclear cells exposed to GBS. Here, we correct that profound abnormality with added IL-17.Conclusion:Our results suggest that profound deficiency of IL-17 production associated with a marked decrease in Th17 cells likely contributes significantly to the increased susceptibility of human neonates to invasive bacterial and fungal infections.