Respiratory distress syndrome (RDS) in premature infants is underscored by the magnitude of Th1 cytokine polarization.

Respiratory distress syndrome (RDS) is a common problem and the leading cause of death in premature infants (PI). The introduction of surfactant treatment for RDS management has lowered mortality and morbidity; nevertheless, some neonates do not improve and are at increased risk of pulmonary hemorrhage. Inflammation, not only local but also systemic, seems to play an important role in the pathogenesis of RDS. To determine whether cytokine patterns characterize RDS and its outcome, we measured type-1 (IL-2, TNF-α, IFN-γ, IL-6) and type-2 (IL-4, IL-5, IL-10, TGF-β1) serum cytokines of 47 PI with established RDS and a control group of 30 healthy, appropriate for gestational age, full-term neonates. Cord blood samples were obtained at the time of delivery from PI and controls. Venous blood samples were collected from PI who received surfactant treatment and/or developed pulmonary hemorrhage. Significantly elevated cord blood cytokine levels were observed in PI at time of delivery, compared to controls, except for IL-5 and TNF-α levels that were within control range. The type-1/type-2 cytokine ratio was significantly increased in PI vs controls. Neonates who developed pulmonary hemorrhage between 2 and 3 days of life and/or died, presented the strongest Th1 and type-1 cytokine polarization that was mainly due to increased IFN-γ and TNF-α, and decreased TGF-β1. The majority of these PI were female with very low gestational age. Overall, PI with RDS present a Th1/type-1 cytokine polarization, which persists irrespective of the treatment provided, and is amplified when complications appear. Th1 polarization is associated with poor prognosis.