Cathelicidins and defensins regulate mast cell antimicrobial activity.

Cathelicidins and defensins are the multifunctional host defense molecules essential for immune response to infection. In recent years they have been shown to be natural, broad-spectrum antimicrobials against both Gram-positive and Gram-negative bacteria, enveloped viruses, and fungi. These small peptides kill the invaded pathogens by destroying their cell membranes and can neutralize biological activities of endotoxin. Apart from exerting direct antimicrobial effects, cathelicidins and defensins can also trigger innate and adaptive defense responses in the host. The functions of the host derived peptides in immunomodulation have been also investigated. Reported activities of these peptides include chemoattractant function, inhibition of neutrophil apoptosis, and ROS production. These peptides directly activate inflammatory cells to production and release of different pro-inflammatory and immunoregulatory mediators, cytokines, and chemokines, however cathelicidins and defensins might mediate the generation of anti-inflammatory cytokines, as well. Insights into the miscellaneous functions of mast cells have exposed that they possess the ability to respond to pathogens and modulate immune response. These immune sentinel cells play a pivotal role in defense mechanisms mainly through the presence of pattern recognition receptors and by release different preformed and newly synthesized mediators and cytokines. The present review provides an introduction to the field of cathelicidins and defensins in general and discusses their impact on mast cells.