New types of clotting factors and defense molecules found in horseshoe crab hemolymph: Their structures and functions

Sadaaki Iwanaga, Shun Ichiro Kawabata, Tatsushi Muta

Research output: Contribution to journalReview articlepeer-review

257 Citations (Scopus)


Invertebrate animals, which lack adaptive immune systems, have developed defense systems, so-called innate immunity, that respond to common antigens on the surface of potential pathogens. One such defense system is involved in the cellular responses of horseshoe crab hemocytes to invaders. Hemocytes contain two types, large (L) and small (S), of secretory granules, and the contents of these granules are released in response to invading microbes via exocytosis. Recent biochemical and immunological studies on the granular components of L- and S-granules demonstrated that the two types of granules selectively store granule-specific 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-lipopolysaccharide (LPS) factor and several tachylectins with LPS binding and bacterial agglutinating activities. On the other hand, S-granules contain various new cysteine-rich basic proteins with antimicrobial or bacterial agglutinating activities, such as tachyplesins, big defensin, tachycitin, and tachystatins. The co-localization of these proteins in the granules and their release into the hemolymph suggest that they serve synergistically to construct an effective host defense system against invaders. Here, the structures and functions of these new types of defense molecules found in the Japanese horseshoe crab.

Original languageEnglish
Pages (from-to)1-15
Number of pages15
JournalJournal of biochemistry
Issue number1
Publication statusPublished - Jan 1998

All Science Journal Classification (ASJC) codes

  • Molecular Biology
  • Biochemistry


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