There was a significant correlation between the proportion of CD14 + cells that were also positive for HLA-DR or CD36, and gestational age. To examine the relationship between the presence of neutrophils and macrophages in the immediate peri-natal period, absolute numbers of these cell Xylometazoline HCl populations were correlated. Cytocentrifuge slides were made from BAL cells within 24 hours of birth and representative images are presented in figure 7. In keeping with figure 1, term infants who were ventilated for non-respiratory problems had few or no neutrophils and low numbers of macrophages, but the latter cells had the classical appearance of alveolar macrophages. Infants with CLD and RDS had more macrophages overall. A qualitative difference between macrophages from CLD and RDS was also Venlafaxine HCl observed, with macrophages isolated from RDS infants appearing larger and more mature. Phenotypic analysis of cells in these patient groups indicated that, as a percentage of macrophages, RDS infants had a higher percentage of CD36 + macrophages yet the overall proportion of macrophages was similar between the two patient groups. A trend for a greater proportion of HLA-DR + macrophages was also seen in RDS compared to control groups but this was not statistically significant. There was no significant difference in percent of CD14+/CD16+ cells in the BAL of CLD versus RDS infants. CLD is a significant cause of morbidity and mortality in preterm infants, with symptoms continuing into adulthood at a great economic cost. Multiple factors occurring both pre- and postnatally contribute to the development of CLD including infection, ventilator induced lung injury, and a persistent inflammatory response. Current therapeutic strategies are of limited benefit, and mostly treat symptoms rather than the causative mechanisms, macrophages are considered anti-inflammatory due to their abilities to secrete anti-inflammatory factors and participate in pathogen handling and efferocytosis.We show preterm infants with resolving inflammatory lung injury have greater numbers of airway macrophages of a differentiated phenotype than infants with progressive inflammatory disease. We also show that prematurity is associated with increased populations of nonclassical, pro-inflammatory monocytes-macrophages in the lung on the day of delivery.