Chemiluminescence activity of phagocytes from tracheal aspirates of premature infants after surfactant therapy.

The effect of surfactant on the respiratory burst of phagocytic cells was studied in the tracheobronchial tract of 40 mechanically ventilated neonates (gestational age 24-37 weeks) over the first week of life. We measured the luminol-dependent chemiluminescence (CL) activity of granulocytes and macrophages isolated from tracheal aspirates in 23 preterm infants 1-6 days after administration of bovine surfactant and in 17 untreated controls. Following stimulation by the chemotactic peptide N-formylmethionylleucylphenylalanine, CL activity was not or only slightly impaired in the surfactant group. In contrast, treatment with exogenous surfactant significantly reduced CL response to opsonized zymosan (OPZ), which involves phagocytosis, for up to 6 days (p < 0.05). The impairment of CL activity seemed to be dose dependent, as repeated surfactant applications (cumulative phospholipid dose of 200 mg/kg) reduced OPZ-elicited CL activity to a greater extent than application of a single dose of 100 mg/kg. In agreement with in vitro studies, our data suggest that high-dose application of exogenous surfactant may affect the antibacterial function of phagocytic cells in the lung.