Human cathelicidin CAP18/LL-37 changes mast cell function toward innate immunity.

The antimicrobial peptide LL-37 is generated from skin keratinocytes during infection of Gram-negative bacteria and exerts a microbicidal effect. LL-37 also causes functional changes in mast cells. Mast cells in the skin are involved in the innate immune system response against microbial infections via Toll-like receptors (TLRs), such as TLR4, which that is known to recognize lipopolysaccharide (LPS), a bacterial component.

Lipoteichoic acid downregulates FcepsilonRI expression on human mast cells through Toll-like receptor 2.

Background: FcepsilonRI on the surface of mast cells (MCs) plays a central role in allergic responses. Recent evidence shows that exposure to microbial components corresponds with a significant reduction in the risk for allergic diseases. Although many reports suggest that this is due to changes in T-cell functions, how MC functions are altered by bacterial infection remains unknown.