Elevated production of interleukin-1-beta from alveolar macrophages isolated from newborn rabbits

Alveolar macrophage (AM) production of pro-inflammatory cytokines has been associated with the development of acute and chronic lung injury. However, the role of AM-derived IL-1 beta in the development of bronchopulmonary dysplasia has not been extensively examined. To determine if in vitro production of IL-1 beta by AM is influenced by maturity, cells were isolated by lung lavage from litters of newborn rabbits and from adults. After overnight incubation in serum-supplemented medium, newborn AM produced more IL-1 beta than cells from adults. When these AM were then exposed for 2 h to endotoxin in serum-free medium, adult cells increased their IL-1 beta secretion while the newborn cells did not. Newborn AM IL-1 beta response to LPS returned by 24 h. AM from newborn rabbits also demonstrated increased spontaneous production and increased LPS-induced production of IL-1 beta during overnight incubation in serum-free medium. The newborn rabbit AM appears to be up-regulated in its IL-1 beta production compared to the adult.