IL1B and meconium aspiration syndrome: The tendency towards increased IL-1β, IL-6 and IL-8 mRNA expression in the natural surfactant group has also previously been shown in vivo for natural surfactant treated animals in a model of experimental meconium aspiration syndrome [9] and for endothelial cell activation in vitro [39] and may be explained by a higher concentration of arachidonic acid in the natural surfactant preparation.