Immunity

Immunity means resistance to disease. It is provided by certain white blood cells, which release antibodies and antitoxins into the blood plasma. Many causative factors can stimulate white cells to produce antibodies antitoxins; for example, microorganisms; bacterial, plant and animals toxins; foreign bodies; transplants; transfusion of incompatible blood cells. All such factors are called antigens. When infection occurs, inflammation results, and part of this defensive reaction involves antibodies and antitoxins. They are present in the blood and help overcome the microorganisms concerned. Some of these antibodies and antitoxins can remain in the blood for life and prevent any repetition of the same infection. Such life-long protection is called acquired immunity; but unfortunately it does not occur for every type of microorganism. However, where immunity is possible it can be reproduced artificially in people who have never been infected by a particular microorganism. It may be done by giving a non-immune person a dose of dead microorganisms. This is called vaccination. Dead microorganisms cannot produce disease but they do stimulate the host’s body to produce antibodies and antitoxins against the particular microorganisms concerned. Thus any subsequent infection with these organisms is immediately overcome by the antibodies and antitoxins already present. If there has been no vaccination or prior exposure to disease, acquired immunity is not present. However, all individuals inherit some degree of natural immunity and this helps explain why some people are more resistant to disease than others.

NOTES

1. inflammation results – наступает воспаление

2. Such life – long protection – Такая защита, имеющая место на протяжении всей жизни

3. dead microorganisms – ослабленные микроорганизмы

4. any subsequent infection – любое последующее инфицирование