Substances & Homeopatic Remedies

Limulus cyclops

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Perhaps the greatest use of horseshoe crabs is found not in their shells, but in their blood. In the early 1950's, scientist Frederick Bang discovered that the blue-colored blood of the horseshoe crab contains special cells that help kill certain kinds of bacteria. When a crab receives a wound, the cells swarm to the area , form a clot, and kill the invading bacteria. Bang was able to separate the chemical in the blood cells that formed clots in the presence of bacteria, which can be harmful to people as well as horseshoe crabs. He called the substance LAL - Limulus amoebocyte lysate. LAL is now used as a fast, effective way of testing drugs to make sure they are free of harmful bacteria before they are given to people. Blood is collected from horse shoe crabs during the summer months, where they are easily caught in the shallow waters off the Atlantic coast from Cape Cod through North Carolina. After collecting some of the blood, the crab is returned to the water. In one bay off of Cape Cod, over 80,000 crabs are bled over the course of a season. Even so, the product is rare enough to be very expensive, up to $15,000 a quart!
Although the adults are released alive, they have approximately a 10% greater mortality than un-bled horseshoe crabs. Horseshoe crabs caught for medical use comprise an additional source of mortality and are not included in the commercial catch statistics.

Besides LAL (the horseshoe crab lacks an immune system; it cannot develop antibodies to fight infection, the components of LAL are part of this primitive "immune" system, they bind and inactivate mcroorganisms) a number of reagents and medically useful compounds have been discovered in the blood of the horseshoe crab.
A new test for fungal infections (G-Test) which is already in use in Japan.
An endotoxin-neutralizing protein which has potential as an antibiotic as well as an alternative endotoxin assay. This protein, ENP, can be made synthetically, which would eliminate the use of live horseshoe crabs for the LAL reagent.
A number of other proteins that show anti-viral and anti-cancer activity.

The dermal glands of the carapace  discharge a viscous secretion onto the surface of the carapace This dermal exsudate (DE) thus contributes to maintaining the cleanliness, and thus the integrity, of the cuticle. Biological investigations have shown a liposome-permeating activity of this DE. As liposomes have become very versatile tools in biology, biochemistry and medicine, the carapace of Limulus cyclops stays in the focus of research. (Liposomes are the smallest artificial vesicles of spherical shape that can be produced from natural untoxic phospholipids and cholesterol. They can be used as drug carriers and loaded with a great variety of molecules, such as small drug molecules, proteins, nucleotides and even plasmids). (8)

Dev Comp Immunol. 1982 Fall;6(4):625-34.
A comparative study on the specificity of Androctonus australis (Saharan scorpion) and Limulus polyphemus (horseshoe crab) agglutinins.
Vasta GR, Ilodi GH, Cohen E, Brahmi Z.

The specificities of Limulus polyphemus and Androctonus australis sera were compared by agglutination and agglutination-inhibition micromethods with human untreated and enzyme-treated peripheral blood cells (erythrocytes, normal lymphocytes and chronic lymphocytic leukemia lymphocytes). Androctonus sera give higher titers than Limulus sera with erythrocytes and lymphocytes. Both sera show more avidity for leukemic than for normal lymphocytes. Limulus sera fail to agglutinate neuraminidase-treated cells but Androctonus sera react with untreated and neuraminidase-treated erythrocytes at the same degree. Sialyl-lactose is the best inhibitor for Androctonus sera, followed by N-acetylneuraminic and N-glycolylneuraminic acids, glucuronic and galacturonic acids, N-acetyl-D-glucosamine and N-acetyl-D-galactosamine. The amounts of inhibitor required depend upon the particular cell and enzyme treatment: agglutination of neuraminidase-treated erythrocytes by Androctonus is inhibited by lower concentrations of the same compounds that inhibit untreated erythrocytes agglutination. Results suggest that although Limulus and Androctonus have specificity for sialic acid containing compounds, on the cell surface, the Limulus receptors might be different from Androctonus receptors.

 Immunol Rev. 2004 Apr;198:106-15.  
A Toll-like receptor in horseshoe crabs.
Inamori K, Ariki S, Kawabata S.
Department of Biology, Faculty of Sciences, Kyushu University, Fukuoka, Japan.

Non-self-recognition of invading microbes relies on the pattern-recognition of pathogen-associated molecular patterns (PAMPs) derived from microbial cell-wall components. Insects and mammals conserve a signaling pathway of the innate immune system through cell-surface receptors called Tolls and Toll-like receptors (TLRs). Bacterial lipopolysaccharides (LPSs) are an important trigger of the horseshoe crab's innate immunity to infectious microorganisms. Horseshoe crabs' granular hemocytes respond specifically to LPS stimulation, inducing the secretion of various defense molecules from the granular hemocytes. Here, we show a cDNA which we named tToll, coding for a TLR identified from hemocytes of the horseshoe crab Tachypleus tridentatus. tToll is most closely related to Drosophila Toll in both domain architecture and overall length. Human TLRs have been suggested to contain numerous PAMP-binding insertions located in the leucine-rich repeats (LRRs) of their ectodomains. However, the LRRs of tToll contained no obvious PAMP-binding insertions. Furthermore, tToll was non-specifically expressed in horseshoe crab tissues. These observations suggest that tToll does not function as an LPS receptor on granular hemocytes.