In the invertebrate, Limulus polyphemus, there exist in the hemolymphs and in the homocytes, a number of molecules with lectin-like activities that may work in concert to serve the role of immunoglobulin in higher animals. Research toward the isolation and molecular characterization of these molecules has been in progress for the last several years in the laboratory. To date, we have identified and completed biochemical, molecular, and functional characterization of several of such molecules including: (1) C-reactive proteins (Limulin), (2) a cell adhesion molecule (Limunectin), (3) an endotoxin-binding protein with protease inhibitory activities (LEBP-PI), and (4) the coagulin (a proteolytic fragment of coagulogen). Each of these molecules are endowed with cell agglutination and adhesion properties and are found as components of extracellular fluid during exocytosis of amebocytes. Binding of these molecules to invading organisms could target them for the pathogenic activities of amebocytes.
