Beta-defensins (also designated BD, and hBD in human) are small cationic peptides with broad-spectrum antimicrobial activity. Produced in mucosal epithelia and neutrophils of several species, Beta-defensins are developmentally regulated. Human b-defensin 2 is locally regulated by inflammation and is the first member of the b-defensin family that is locally inducible by inflammation. The murine homolog of human b-defensin 2, which is called b-defensin 3, is present in the respiratory system and in low levels in the epithelial cells of the intestine and lung. The unique murine b-defensin 2 (Defb2) is not expressed in airways of untreated mice, but is upregulated in the airways by lipopolysaccharide and may contribute to host defense at the mucosal surface of the airways