A lectin that targets specific bacteria for killing on DNA-based extracellular traps

Animal defenses directed against bacteria include DNA-based extracellular traps (ETs) that are produced by innate immune cells. ET-bound bacteria are prevented from further tissue dissemination and are eventually killed by ET-bound antibacterial proteins. It is unclear how bacteria bind to ETs, though it has been proposed that the negatively-charged DNA scaffold of the ETs is involved. We have found that the bacterial-binding lectin CadA is a component of the ETs produced by the innate immune cells of Dictyostelium discoideum and is required for the binding and killing of two Enterobacteriaceae by ETs, but not other bacteria. Our results suggest that ETs selectively sequester bacteria and that lectins can facilitate bacterial killing by acting as ET-bacteria binding proteins.