Serum, << SIHR uhm, >> is the clear, fluid part of the blood that is left after a clot forms. Serum is just like plasma (the total liquid part of the blood) except that serum does not contain fibrinogen, a substance that causes clotting.
Serum contains such substances as salt, proteins, glucose, and fats. Samples of serum are used to help diagnose (determine) the medical problems of patients. Tests on blood serum are called serologic tests.
Serum proteins contain antibodies that the body produces to fight certain diseases and toxins (poisons). A serum containing antibodies that is taken from a person or animal and injected into a patient is called an antiserum. Antiserums work against such diseases as diphtheria and tetanus (lockjaw). Antitoxins are certain kinds of antiserums.
Serum taken from a person who has recently recovered from a disease usually contains more than the normal amount of antibodies. This serum may help cure or prevent the disease. However, doctors have found a more efficient way of providing disease-fighting antibodies. Instead of using the entire serum, they inject only a part of the serum called gamma globulin. Gamma globulin is a class of proteins that contains most of the blood’s antibodies. Gamma globulin preparations are used to fight and prevent hepatitis, measles, mumps, and whooping cough.
Serum obtained from animals is easier to obtain and costs less than serum from human beings. But it is often less effective and more dangerous than human serum. A horse is usually used because it has a large amount of blood and produces many antibodies. Horse antiserums are used to prevent rabies and to treat persons bitten by venomous snakes and black widow spiders. They are also used to treat botulism (food poisoning), gas gangrene, and rabies. However, some patients are allergic (extremely sensitive) to animal proteins, and may have serious reactions.
See also Antitoxin; Blood transfusion; Gamma globulin; Plasma.
