SLPI and bronchopulmonary dysplasia: In premature human neonates requiring manual respiration, the proportion of SLPI to its neutrophil-derived proteases was indicative of the development of bronchopulmonary dysplasia (BDP): neonates who developed BDP had a lower SLPI inhibitory capacity (80, 81) or a lower ratio of SLPI to its protease targets (82).