The blood of the animals we see is mostly red, while the blood of Limulus is blue. Why? When mammals breathe, they inhale oxygen into the lungs and exchange gas with the blood in the alveoli. Then, oxygen is carried by the blood into the heart and flows to the whole body through the artery for metabolism. Mammalian blood carries oxygen, which is "carried by iron in the blood". The combination of iron and oxygen turns red, so the blood turns red. In the blood of lower animals such as tachypleus amebocyte lysate, copper is used instead of iron to "transport" oxygen. Because copper containing protein conjugates are blue, this makes their blood blue.
The blood of tachypleus amebocyte lysate is not only special in color, but also magical in function. The blood cells of tachypleus amebocyte are very primitive, there is no division of labor, and there is only one kind of deformed cells, but this simple and primitive blood has magical functions. When the toxin of bacteria comes into contact with the blood of tachypleus amebocyte lysate, the deformed cells in the blood of tachypleus amebocyte lysate will release a coagulation protein, which will lead to the rapid coagulation of blood and make the bacteria unable to reproduce. Then, the blood will form a barrier to prevent the invasion of other bacteria.
In the 1850s, scientists extracted a coagulant called tachypleus amebocyte lysate from the blue blood of tachypleus amebocyte lysate. This tachypleus amebocyte lysate can not only immediately check whether the patient is infected by bacteria and make a rapid diagnosis for the diagnosis and treatment of emergency patients, but also a simple and reliable method to detect whether there are pathogens in drugs and medical supplies. The vaccine we inject must pass the test of tachypleus amebocyte lysate. If the tachypleus amebocyte lysate reagent is immediately solidified or discolored, it indicates that the injection contains pathogenic bacterial endotoxin; If the reagent does not solidify, the vaccine is safe. Tachypleus amebocyte lysate is also widely used to detect whether drinking water, milk, canned food and other foods are contaminated by bacteria.