Bactericidal factor in human airway surface fluid and uses thereof

A bactericidal factor isolated from the surface fluid of airway epithelial cells and uses therefore is described. The bactericidal factor is characterized as having the following features: a) a molecular weight of less than 10 kd; b) heat stable; c) broad spectrum activity including gram positive and gram negative bacteria, fungi, and methicillin resistant Staphylococcus; and d) decreased antimicrobial activity in increasing salt concentration.