What Is Immunity?

Immunity (lat. Immanitas – liberation from duties) is an ability of body to resist infections and toxins. Immune system is most important system in human body. Immunity protects body not only from microbes that provoke infectious diseases but also from genetically foreign cells (parasites, enthetic tissues and even cancerous cells). Immunity to infectious diseases shows in several forms.

Natural immunity appears without conscious human intervention. It may be innate or adaptive.

1. Innate immunity (inherent immunity) is determined by characteristics transmitted heritably which are common to particular species. This is biological peculiarity of a specie which is resistant to particular infections. For example, humans never get infected with distempers and, instead, dogs never get infected with typhoid fever. Children in their first months of life have natural immunity to measles, scarlet fever, and diphtheria, which is connected with retention of protective antibodies that he got from mother who was diseased with them in past.

2. Adaptive immunity (acquired immunity) results from body reaction to entering of microbes in the body. It occurs after infectious disease or results from latent inflammatory process. Acquired natural immunity after ones infectious disease persists for a long time, sometimes for life (typhoid fever, chicken pox, measles, etc), and sometimes for a short time (influenza, etc). Immune system “remembers” all microorganisms which it faced before. Antibodies against them remain in the body for a long time or even for life. So when the microbe enters the body again, the immune system already knows how to fight it and as a result the disease courses in more mild form.

3. Artificial immunity appears after injecting vaccines or serum. Vaccination is performed routinely independently from morbidity rate. Serum with antibodies is used to provide rapid activation of immunity when infection has already occurred. The duration of artificial immunity is less than of natural immunity. Serum provides the duration of 2 – 3 weeks, and vaccines from several months to 5 – 8 years.

Obligatory vaccines are vaccines against tuberculosis, measles, poliomyelitis, diphtheria, tetanus, etc. Routinely are made vaccines to particular population groups, for example, vaccines against intestinal infections to workers of food enterprises, child-care centres, etc. In particular terms vaccines are made again (revaccinaction).