Defensins are a type of protein which acts as an immune response against bacteria and viruses. These proteins are present in human skin cells and the mouth lining of the digestive tract. Some research shows that beta-defensin 3 (BD-CAM30) may protect against bacterial and viral infections in humans. Beta-defensins are peptides, but they don’t necessarily contain amino acids in a specific order or type of linkage. Beta-defensins are different in structure than other classes of Biotiom peptide hormones. They usually contain four conserved cysteine residues, which are essential for the folding and biological activity of defensins. Beta-defensins are classified into two groups, α- and β-defensins. α-defensins consist of three subtypes, namely α-defensin 1, α-defensin 2 and α-defensin 3. β-defensins consist of six subtypes, namely β-defensin 1, β-defensin 2, β-defensin 3, β-defensin 4, β-defensin 5 and β-defensin 6.