A component of horseshoe crab blood helps identify toxins in IV drugs.
Bizarre though it may seem, the horseshoe crab plays a vital role in detecting the presence of toxins in vaccines and other drugs administered by injection. The horseshoe crab's blue blood contains amebocytes, which it uses to fight infection instead of the white blood cells used by vertebrates. From these amebocytes, a laboratory can extract Limulus Amebocyte Lysate (LAL), and use it to detect the presence of certain bacteria.
Endotoxins
LAL is our primary means of detecting endotoxins, which are the part of some bacteria to which our immune systems react, causing fever and inflammation. Because endotoxins can remain even after sterilization of a drug meant for injection, screening for their presence reduces the chance of an adverse reaction in a patient.
History
The sensitivity of horseshoe crab blood to endotoxins was discovered in the 1960s by Dr. Frederik Bang at John Hopkins University. Collaborating with Dr. Jack Levin, he devised the basic procedure for extracting LAL from horseshoe crab blood that remains mostly unchanged to this day.
Collection
The crabs are released after their blood is extracted, and 85 to 97 percent survive.
Because horseshoe crabs are such a valuable medical resource, care is taken in obtaining their blood. Clam rakes or dredges capture the crabs, and they are trucked to a laboratory. There, up to 30 percent of their blood is removed, which they can replace in about a week. They are then returned to the wild, and not bled again by LAL manufacturers for another year.
Other Medical Uses
The ability of LAL to detect endotoxins can also be employed to rapidly detect the presence of urethral or spinal infections, or to test the quality of food, air or water. Additionally, new research suggests uses for other components of horseshoe crab blood, which may prove to be effective agents for fighting fungus, viruses and cancer.
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