Cathelicidins: an ancient family of fish antimicrobial peptides

Cathelicidins are an important family of antimicrobial peptide effectors of innate immunity in vertebrates. While their mammalian counterparts have been extensively characterized in the last two decades, data on fish cathelicidins has only recently been gathered. This chapter covers the available recent insights on fish cathelicidins regarding their evolution, protein structures, gene expression, antimicrobial and immunomodulatory properties, highlighting the similarity and the differences with the mammalian ones. Genes of fish cathelicidins have been shown to be highly responsive to bacteria; moreover, experimental data suggest both direct antibacterial activity and modulation of other immune effectors. These functions, which still need to be fully characterized, indicate cathelicidins as an important and effective defense line in fish