BACKGROUND: Human cathelicidin LL-37 shows activity towards both gram-positive and gram-negative bacteria, and it is also active against some types of viruses. Besides its antimicrobial effects, the peptide modulates innate immunity through binding and inactivation of bacterial endotoxins and promoting chemotaxis of immune cells. RESULTS: LL-37 is reported to interact with plasma membrane receptors and mediate import of Ca CONCLUSIONS: Altogether, LL-37 may inhibit and prevent the infection from spreading by direct anti-bacterial and anti-viral effects, but also via anti- and pro-inflammatory mechanisms, and through killing already infected and weakened host cells at the site of infection/inflammation.