“…This basal animal is strategically placed in the phylogenetic lineage and is a good model to study unresolved questions regarding antimicrobial peptides in primitive vertebrates. The nurse shark's natural antibodies, spontaneous cytotoxicity, and complement have been studied, and are believed to work in concert to form an immunosurveillance system seeking out new antigens (Rudikoff et al 1970;Clem et al 1982;Pettey et al 1983;Smith et al 1986;Flajnik 1994;Parham 1995). In addition, innate system components such as antibacterial proteins/peptides and other antimicrobial substances may form the basis of innate immunity necessary to maintain a healthy animal, particularly during times of stress.…”