Activities of antimicrobial peptides. As well as their antimicrobial function (1), antimicrobial peptides have other potential roles in inflammation and infection (2,3). The mechanism of the antimicrobial activity is explained in the insert. After electrostatic interactions between the negatively charged bacterial wall and the positively charged peptides (a), the peptide associates with the membranes, either by insertion as pores (b) or by forming carpet-like structures that lead to a destabilization of the membrane. The sources (1) of antimicrobial peptides in the airways are epithelial cells and inflammatory cells. Defensins and LL-37 have a feedback mediator function that targets these cell types (2,3), influencing the release of mediators and other cellular processes such as proliferation and chemoattraction.