Defensins are small cysteine-rich cationic proteins found in both vertebrates and invertebrates. They're active against bacteria, fungi and many enveloped and nonenveloped viruses. They consist of 18-45 amino acids including six (in vertebrates) to 8 conserved cysteine residues. Cells of the immune system contain these peptides to assist in killing phagocytized bacteria, for example in neutrophil granulocytes and almost all epithelial cells. Most defensins function by binding to microbial cell m… (More on Defensin)