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13.5.2. Artificial immunity

Artificial immunity

This type of immunity is acquired artificially through the use of medical techniques. It can be, in turn, passive or active:

Passive artificial immunity: serum therapy

The passive artificial immunity is the introduction into the organism of antibodies previously synthesized by another individual. The fluid therapy is to introduce the antigen corresponding to an animal (usually the horse was used), which synthesizes antibodies against a particular disease. After extraction of the animal's blood, the antibodies to be injected into the infected person are isolated and purified. They can also be drawn from the blood of another person who has overcome the infection.

Although horse serum has been used, thanks to genetic engineering, it is now possible to use genetically modified microorganisms that produce specific antibodies against the pathogen.

Some of the advantages of serum therapy are:

  • It provides immediate protection (within hours of injection), while vaccines require several days to produce resistance.
  • It is useful in people with deficiencies in their immune system, since they do not need to synthesize their own antibodies.

Some of the drawbacks of serum therapy are:

  • Immunity only lasts a few months, so it is a limited duration , which ends when the administered antibodies disappear.
  • When the antibodies come from the serum of an animal, rejection reactions can occur against it, which is why monoclonal antibodies obtained by Biotechnology are currently used.

Fluid therapy is used for curative purposesThere are serums for rapidly developing infectious diseases such as tetanus, rabies, and diphtheria.

Active artificial immunity: vaccines

The artificial immunity active is achieved by vaccination, which consists in introducing dead or attenuated bacteria incapable of developing the disease, but who are carriers of antigens specific. Then, the body responds by making antibodies (primary response) and is immunized against the disease, since, when there is a new contact with the antigen, the secondary response will be triggered, so the infection will not occur .

The duration of this immunity can be lifelong or temporary.

The purpose of vaccination is not to cure, but to prevent a disease, since the effect of vaccines occurs a few days later, when the body makes the antibodies .

Vaccines are a good method to fight infectious diseases, some of them being eradicated, such as smallpox. But you can't always get the right vaccinations. Research is currently underway to produce vaccines against HIV or hepatitis C virus, but the genomes of these viruses have a high mutation rate and have not yet been produced. In the influenza viruses they are also very frequent mutations, so the variation of its antigens prevents permanent protection against them.

Types of vaccines

Several types of vaccines are distinguished, depending on the origin and nature of the antigens:

  • Live vaccines. These vaccines have live microorganisms, but very weakened, so they reproduce in the inoculated individual but causing a very small infectionThe body has no problem deactivating this infection, since it generates a large amount of antibodies and memory B lymphocytes, which gives it long-lasting immunity. Examples of live vaccines are poliomeasles, and rubella.
  • Inactivated vaccines. In these vaccines, the  inoculated microorganisms are dead, so they cannot reproduce in the body. The immune system response is weaker than with live vaccines, so additional booster doses are necessary to stimulate memory B cells and maintain immunity. The inactivation of microorganisms occurs with chemicals, such as formaldehyde, or with the application of heat or radiation. Examples of this type of vaccine are rabies , typhoid , whooping cough, and diphtheria.
  • Acellular vaccines . Instead of containing microbes, weakened or dead, they have only products or parts of the micro-organisms , with the antigens that most stimulate the immune system. They are distinguished:
    • Toxoids. They are bacterial toxins altered (inactivated or non-toxic) by the effect of heat or chemical agents, but which retain the ability to stimulate the production of antibodies. Vaccines of this type are tetanus and diphtheria.
    • Isolated antigens. Sometimes just a viral coat protein (which acts as an antigenic determinant ) is capable of eliciting an immune response.

Fundamental ideas about vaccination and fluid therapy

The vaccines are preventive (not curative). In vaccination, attenuated antigens are inoculated that trigger the appearance of B lymphocytes and memory cells, which allows immunity to be maintained for a long time. It is a type of active artificial immunity.

The fluid therapy is curative (not preventive). In serum therapy, antibodies of external origin are transferred , so memory cells are not formed and their duration is very limited (a few months). It is a type of passive artificial immunity.

Differences between vaccination and serum therapy
Vaccination Serum therapy
Active artificial immunization Passive artificial immunization
Contains attenuated antigens Contains specific antibodies
Create immune memory Does not create immune memory
It takes a few days to be effective Elicit an immediate response
Preventive effect Healing effect
Long lasting effect Short lasting effect