Immunity (medicine)

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Immunity ( Latin immunitas for 'freedom from something' in relation to health, 'freedom from disease', 'immunis' as an adjective for 'immune to / free from') is the security acquired through contact with a pathogen or its toxins (Insensitivity or insensitivity) of the organism to specific external attacks or the ability of the organism to eliminate certain pathogens without symptoms .

Immunity can be acquired through immunization or vaccination . One differentiates the active immunization of passive immunization . Active immunization options are earlier immunization with virulent pathogens (see also Variolation ), active vaccination with weakened pathogens ( live vaccine ), active immunization with inactivated (killed) pathogens ( dead vaccine ) and active immunization with toxins (see dead vaccine properties ) or toxoids ( toxoid vaccine ).

Physiological basics

Whether or not contact with a pathogenic microorganism or molecular complexes leads to a disease depends not only on the severity and virulence of the infection but also on the protective powers of the organism.

The first line of defense is the skin or mucous membrane, which is particularly vulnerable in infants . Their protection is increased by the mechanical and chemical action of the secretions .

In the case of a protective effect through antibiosis , the inhibiting or killing effect on the bacterial flora of an organism can lead to an incorrect colonization with resistant pathogens. Are z. B. If certain bacteria are suppressed by antibiotics , others, such as resistant staphylococci or fungi , can multiply unchecked and become pathogenic.

If an invasion of pathogens has taken place, the further course depends on the immunity of the organism. A distinction is made between inherited immunity of a non-specific and specific type and acquired immunity. The inherited one can be permanent, so the complete immunity of humans against certain animal diseases, or also temporary, z. B. the immunity of the newborn to scarlet fever .

The individual infectious diseases immunize very differently; some produce lifelong immunity, e.g. B. the measles , while others, e.g. B. scarlet fever, give a good, but not entirely reliable protection, which is why repeated diseases can occur. In the case of dengue fever , protective antibodies against the infecting subtype are produced, but if the infection is renewed by a dengue virus of the three other subtypes , these have an intensifying effect and increase the pathogenicity.

Certain acute infectious diseases such as measles, diphtheria , scarlet fever and the like. a. are also called infectious childhood diseases because children get it more often than adults.

Types of immunity

  • Anti-Infectious Immunity
is the insensitivity to disease-causing ( pathogenic ) microorganisms.
  • Antitoxic Immunity
is the protection against endo- or exotoxins as well as against vegetable or animal poisons.
  • Nonspecific immunity
is to be rated as natural resistance . For example, foot and mouth disease or classic swine fever cannot be transferred to humans. This also means the physical or biological protective mechanisms of the organism, such as the skin-mucous membrane barrier.
  • Adaptive immunity
is also known as acquired immunity. The term “specific immunity” is also incorrectly used, but the mechanisms of innate immunity are also specific (see also specificity ). In embryos and infants, it is mainly transmitted from the mother via the placenta or through breast milk , and later acquired through protective vaccinations or through the disease itself.
  • Innate immunity
exists since birth and was mostly reached via the placenta by antigens / antibodies from the mother.
  • Natural immunity
is genetically determined by the presence of natural antibodies without previous contact with pathogenic germs or other substances harmful to the organism.
  • Paraimmunity
is the artificially acquired immunity or increased preparedness for a short period of time (usually 1–2 weeks). Paraimmunity can be acquired through weakened bacterial or viral components, herbal or synthetic extracts.
  • Premunity
exists when a person carries living pathogens and passes them on, but does not develop them himself (for example with malaria ).
  • Cross immunity
An infection with one of several types of pathogens protects against further infection with one of the other types after the infection has been overcome. A well-known example is cowpox , the infection of which also offers protection against smallpox . The unspecific cross-immunity in the formation of isoagglutinins is also important . The isoagglutinins are formed around the first six months of life in contact with antigens of bacterial origin, which are similar to the AB0 antigens (AB0 system of the blood groups). Since no antibodies are normally formed against the body's own characteristics, the antibodies that correspond to one's own blood group are missing .
  • Humoral immunity
The humoral immune response produces antibodies that bind to infected cells and pathogens . Anti-infection antibodies are called neutralizing antibodies .
  • Cellular immunity
In the cellular immune response , cytotoxic T cells attack and destroy infected body cells. They respond to antigens found on the cell membrane of some cells in the body.

See also


Individual evidence

  1. Karl Wurm, AM Walter: Infectious Diseases. In: Ludwig Heilmeyer (ed.): Textbook of internal medicine. Springer-Verlag, Berlin / Göttingen / Heidelberg 1955; 2nd edition ibid. 1961, pp. 9-223, here: pp. 56 f.