At the interface of innate and adaptive immunity, antimicrobial (host defence) peptides have been shown to enhance the overall immune response, where peptide expression and activity map onto aspects of the response to infection. This includes the ability to chemoattract phagocytic and antigen-presenting cells, and regulate the host cytokine response. After two decades of basic research, the effects of peptides on B and T lymphocyte function, including B cell activation and antibody production, cytotoxic T cell and natural killer cell killing, and T helper cell function, are starting to demonstrate that some of these peptides are capable of directing a prolonged cellular and humoral response to a pathogen. As a spin-off from such fundamental studies, the commercial properties of some antimicrobial (host defence) peptides have been recognised. From these, attempts to characterise and exploit natural peptides, and design new analogues have identified a number of potentially valuable antimicrobial molecules. There is a huge world-wide demand for compounds with novel properties, capable of addressing emerging antibacterial resistance in the clinic.(source: www.regonline.co.uk)