A human body needs a guardian that protects it from numerous harmful influences of the environment. The immune system plays the role of such a guardian. The word ‘immune’ means ‘untouched’ or ‘free’ from something. This is the most complex system in the human body that consists of different organs, the nervous system, proteins and cells. All the system components work together and their smooth work help people stay healthy and resist pathogens, e.g. a bacterium, virus, or other microorganisms that can cause a disease. However, sometimes the immune system cannot help, for instance in case of an aggressive pathogen or the one that the body did not have contact previously.
The immune system performs the functions of neutralizing viruses, bacteria and fungi; it recognizes potentially harmful substances that get inside the body from the environment; and provides support necessary to fight somehow changed cells, e.g. cancerous cells.
The ability of the immune system to recognize ‘self’ and ‘non-self’ substances ensures effective protection of the organism. The body fights ‘non-self’ substances and does not attack its own healthy ‘self’ cells. The former are called antigens, they are the proteins of the pathogens. The defensive cells can detect these proteins and cause a series of specific processes in the cells. However, sometimes the system fails and identifies the ‘self’ cells as ‘non-self’, so an autoimmune reaction takes place.
An outstanding fact is that the human body ‘remembers’ which proteins are dangerous. There are two parts of the immune system, namely the innate and adaptive. The innate immune system is responsible for the general defense; it targets non-specific pathogens, especially different bacteria. Genetic factors influence the human immune system; they play a vital role and protect the infants until their adaptive immune system becomes well developed. Human genes define the number of major histocompatibility complex molecules that the cells carry. Some of them are believed to deal with the autoimmune diseases.
The adaptive immune system creates antibodies, special agents that are learnt to respond in a special way. It is developed after the organism has overcome a certain disease. In the future, the immune system will respond faster and more efficiently. Therefore, the human body can adopt and learn new things. However, both systems work together and complement to each other. Moreover, people can influence the condition of their immune system. For example, immunization helps the cells to recognize pathogens and fight them more efficiently.
So, immune system should function properly in order to maintain an overall health. People should avoid stress, have a balanced diet, sleep enough, do sports, and drop smoking. Therefore, they will not weaken their immune system and live a longer and healthier life.