Defensins (alpha and beta) are cationic peptides with a broad spectrum of antimicrobial activity that comprise an important arm of the innate immune system. The alpha-defensins are distinguished from the beta-defensins by the pairing of their three disulfide bonds. To date, four beta-defensins have been identified; BD1, BD2, BD3 and BD4. beta-defensins are expressed on some leukocytes and at epithelial surfaces. In addition to their direct antimicrobial activities, they are chemoattractant towards immature dendritic cells and memory T cells. The beta-defensin proteins are expressed as the C-terminal portion of precursors and are released by proteolytic cleavage of a signal sequence and, in the case of BD1 (36 a.a.), a propeptide region. beta-defensins contain a six-cysteine motif that forms three intra-molecular disulfide bonds. MW: 5.54 kDa. Purity >98% pure by SDS-PAGE and HPLC analyses.