REVIEW Antimicrobial peptides: General overview and clinical implications in human health and disease Eduardo Guaní-Guerra a, ⁎ , Teresa Santos-Mendoza b , Saúl O. Lugo-Reyes b , Luis M. Terán b a Department of Immunology, Hospital Regional de Alta Especialidad del Bajío, León Guanajuato, Mexico b Department of Immunogenetics, National Institute of Respiratory Diseases (INER), Mexico City, Mexico Received 29 November 2008; accepted with revision 9 December 2009 Available online 29 January 2010 KEYWORDS Antimicrobial peptides; Defensins; Cathelicidin; Innate immunity; Host defense Abstract Antimicrobial peptides (AMPs) are evolutionarily conserved molecules involved in the defense mechanisms of a wide range of organisms. Produced in bacteria, insects, plants and vertebrates, AMPs protect against a broad array of infectious agents. In mammals these peptides protect against bacteria, viruses, fungi, and certain parasites. Recently, novel biologic effects of AMPs have been documented such as endotoxin neutralization, chemotactic and immunomodu- lating activities, induction of angiogenesis and wound repair. Thus these ancestral molecules are crucial components of the innate immune system and attractive candidates for novel therapeutic approaches. This review focuses on cathelicin and defensins, the most documented human AMPs, and discusses their antimicrobial activity and pleiotropic immunomodulating effects on inflammatory and infectious diseases. © 2009 Elsevier Inc. All rights reserved. Contents Introduction............................................................. 2 AMPs in humans .......................................................... 2 Cathelicidins........................................................... 2 Defensins ............................................................ 2 Expression and regulation ..................................................... 4 Functions of AMPs ......................................................... 4 Mechanisms of antimicrobial activity ............................................. 4 Immunomodulatory properties................................................. 4 Abbreviation: AMPs, antimicrobial peptides. ⁎ Corresponding author. HRAEB: Hospital Regional de Alta Especialidad del Bajío, Blvd. Milenio 130 San Carlos La Roncha C.P. 37660 León, Guanajuato, Mexico. E-mail address: eduardoguani@yahoo.com.mx (E. Guaní-Guerra). 1521-6616/$ – see front matter © 2009 Elsevier Inc. All rights reserved. doi:10.1016/j.clim.2009.12.004 available at www.sciencedirect.com Clinical Immunology www.elsevier.com/locate/yclim Clinical Immunology (2010) 135,1–11