Clotting and Immune Defense in Limulidae

Abstract
The evolution of an effective system for microbial defense is central to the survival and perpetuity of higher organisms. Invertebrates, which lack typical immune systems, have developed unique systems to detect and respond to microbial surface antigens, such as lipopolysaccharide (LPS), peptideglycan, and β-(l,3)-glucan. Because both invertebrates and vertebrate animals respond to these substances, it is likely that a system recognizing these epitopes emerged at a very early stage in the evolution of these animals.