Cathelicidins comprise an important family of antimicrobial peptides that are essential for protection of skin against bacterial infection in mice (Nizet et al., 2001), and are relevant to infection in human skin diseases such as atopic dermatitis (Ong et al., 2002). The human cathelicidin gene (Camp) is expressed as an inactive precursor protein (hCAP18) and is present in neutrophils, mast cells, keratinocytes, and eccrine glands (Braff et al., 2005). hCAP18 consists of an N-terminal signal peptide, a cathelin domain, and a C-terminal region encoding the antimicrobial domain (Sorensen et al., 2001). After proteolytic processing of hCAP18 to peptides such as LL-37, the peptide exerts antimicrobial activity that protects the host from infection. In this study we determined if cathelicidin is produced by sebocytes, thereby establishing its potential to add to defense of the skin by this cell.

The sebaceous gland has been suspected to provide protection to the external skin surface, but its functions were only recently understood (Zouboulis, 2003). Lipids produced by the sebocyte exhibit antibacterial activity (Georgel et al., 2005) and peptides of the β-defensin family have been found in human pilosebaceous units (Chronnell et al., 2001). Since cathelicidin has synergistic activity with β-defensins, it was of interest to determine the expression of cathelicidin in the sebaceous gland.