The study shows that the antimicrobial peptide LL‑37, part of the body’s natural defense, is present in human saliva and that its mouse counterpart is made in salivary glands and mouth lining. This means our mouths already have a built‑in antibiotic that helps keep harmful microbes at bay.

The expression of antimicrobial peptides at epithelial surfaces such as skin, lung, and intestine is thought to provide protection against infection. Cathelicidin antimicrobial peptides are essential for the protection of skin against invasive bacterial infection. To determine if cathelicidins are also present in the oral cavity, we examined the expression of both mRNA and protein in mice and human saliva. The murine cathelicidin (CRAMP) was detected in the adult by reverse-transcription/polymerase chain-reaction (RT-PCR), and in embryonic, newborn, and adult tissues by in situ hybridization and immunohistochemistry. CRAMP mRNA and protein were localized to the salivary glands, specifically in acinar cells of the submandibular gland and palatine minor glands, as well as in lingual epithelium and palatal mucosa. In man, the human cathelicidin LL-37 was detected in human saliva by Western blotting. These results indicate that cathelicidins are present in the salivary system, in some oral epithelia, and in saliva, contributing to broad-spectrum defense of the oral cavity.