LPS priming of adult and neonatal PMN. LPS priming activity was assessed using LPS mixed with HBSS (□), adult plasma (⊠), and newborn plasma (▪) in combination with adult or newborn PMN. LPS primed PMN were triggered to produce CL activity by the addition of fMLP and oxidative radical production was assessed using luminol (Sigma Chemical Co) with a CL assay. Activity for cells triggered with fMLP in the absence of LPS priming was consistently less than 5 CL units in this experiment. *P < .0005 adult PMN with adult plasma (n = 12) compared to adult PMN with newborn plasma (n = 12), and neonatal PMN with adult plasma (n = 12) compared to neonatal PMN with newborn plasma (n = 12). +P < .05 adult PMN versus newborn PMN.