NEW TYPES OF CLOTTING FACTORS AND DEFENSE MOLECULES FOUND IN HORSESHOE-CRAB HEMOLYMPH - THEIR STRUCTURES AND FUNCTIONS

Invertebrate animals, which lack adaptive immune systems, have develop ed defense systems, so-called innate immunity, that respond to common antigens on the surface of potential pathogens, One such defense syste m is involved in the cellular responses of horseshoe crab hemocytes to invaders, Hemocytes contain two types, large (L) and small (S), of se cretory granules, and the contents of these granules are released in r esponse to invading microbes via exocytosis, Recent biochemical and im munological studies on the granular components of L- and S-granules de monstrated that the two types of granules selectively store granule-sp ecific proteins participating in the host defense systems, L-granules contain all the clotting factors essential for hemolymph coagulation, protease inhibitors including serpins and cystatin, and anti-lipopolys accharide (LPS) factor and several tachylectins with LPS binding and b acterial agglutinating activities, On the other hand, S-granules conta in various new cysteine-rich basic proteins with antimicrobial or bact erial agglutinating activities, such as tachyplesins, big defensin, ta chycitin, and tachystatins. The co-localization of these proteins in t he granules and their release into the hemolymph suggest that they ser ve synergistically to construct an effective host defense system again st invaders, Here, the structures and functions of these new types of defense molecules found in the Japanese horseshoe crab (Tachypleus tri dentatus) are reviewed.