Abstract 79

Background/Aim: T cells secrete a number of cytokines with hemopoietic activities. IL-17 is a newly described cytokine secreted by activated CD4+ T cells. In vitro, IL-17 supports the growth of hematopoietic progenitors; in vivo, IL-17 can stimulate granulopoiesis. Recent studies have shown activation of CD4+ T cells in neonates with sepsis. However, whether IL-17 increases following bacterial infections or if peripheral neonatal activated T cells are able to produce IL-17 is presently unknown. Subjects: As a step toward making such determinations, we examined IL-17 expression in the plasma, urine, and lung fluid of 13 sick neonates and in the plasma and urine of 7 healthy babies admitted to a NICU. Results: In all samples of control neonates as well as of those with inflammatory non infectious disease, IL-17 concentrations (ELISA, R&D system) were under the minimum detectable dose. Among infected neonates, IL-17 was present at measurable concentrations in the majority of lung fluids obtained coincident with pneumonia, but not in the plasmas or urines of those who had sepsis or urinary tract infection (both of which with gram-bacteria). We therefore tested in vitro whether endotoxin could stimulate IL-17 production from neonatal T cells. T cells separated from cord blood mononuclear cells were incubated 48 hrs with LPS or B7 in the presence of either unprimed autologous monocytes or monocytes previously primed with LPS. In neither condition was IL-17 detectable. Yet, when T cells were incubated with PHA, a polyclonal T cells activator, high concentrations of IL-17 were found in the culture media. Conclusions: Based on these preliminary results, neonatal T cells are able to express IL-17 upon activation. Gram-bacteria do not appear to be effective stimuli for IL-17 production. The expression of IL-17 in other infectious conditions is being investigated.