The term immunity comes from Latin and means “freedom from disease.” From a medical point of view, this means that an organism, such as a human being, is immune to external attacks by pathogens. Even simple organisms have a so-called immune defense. This is similar to the protective mechanisms that plants also have. Vertebrates, which include humans, have far more complex immune defenses than plants and simple organisms.
What is immunity?
Acquired immunity occurs after a single infection with a pathogen. A classic case is chickenpox. In most cases, the disease occurs only once in a lifetime, as affected individuals become immune to the virus after the outbreak. Immunity manifests itself in different ways in people. Genetic immunity protects affected individuals from certain viruses for life. It is most likely caused by a mutation in the genetic material. Approximately 0.5% of all people have natural immunity to HIV, for example, and innate resistance to leprosy also exists. Acquired immunity, on the other hand, develops after a single infection with a pathogen. A classic case is chickenpox, which, although considered a childhood disease, can also occur in adults. In most cases, the disease occurs only once in a lifetime, as those affected become immune to the virus after the outbreak. Only in exceptional cases, i.e. when the body’s own defenses are severely damaged, do affected individuals contract chickenpox more than once. Acquired immunity to an antigen can also lead to cross-immunity. In this case, the body develops resistance to a related antigen. Newborns have innate immunity, but it lasts only temporarily. In their first months of life, so-called nest protection protects them from some diseases to which their mother is immune. However, the natural protection acquired through the baby’s bloodstream wears off after a while and disappears completely after about nine months. After loss of natural immunity, vaccinations provide protection against pathogens. Vaccination creates a natural immunity that needs to be refreshed after a few years.
Function and task
Immunity to external attack has safeguarded human life since the dawn of history. Without immunity and resistance to disease, humans would fall victim to seemingly harmless illnesses, such as the common cold. Only through immunity is it possible for humans to ingest food and drink water. Every everyday action places demands on the immune system, and self-evident processes such as breathing or touching everyday objects, plants and animals require a certain degree of immunity to harmful substances. Without this vital defense, pathogens and microorganisms can invade the human body and cause tissue damage. In addition, the immune system protects humans from the body’s own attacks, which can be triggered by faulty or dead cells, for example. Human immunity is a complex protective mechanism granted by the interaction of various barriers. The largest external barrier in humans is the skin, which prevents the penetration of harmful substances. Other external barriers that support immunity are the mucous membranes, the respiratory tract, the eyes, the oral cavity and the urinary tract. The intestine is often said to have a special function in the body’s defense. At the cellular level, the granulocytes found in the bloodstream and the macrophages known as giant cells guarantee natural protection against invaders and also promote the breakdown of toxic substances. Other active substances in the body’s defense system include natural killer cells, dendritic cells, T-helper cells and antibodies. Without the interplay of these mechanical barriers, cells, and messengers, even everyday illnesses and infections become deadly risks.
Diseases and ailments
Diseases and disorders of the immune system, just like immunity, can be either congenital or acquired. Congenital disorders of the immune system are very rare and in many cases are fatal in infancy and early childhood. Therapy is difficult because only treatment with stem cells from another person is considered promising.Another way to protect the sick is to try to keep them away from sources of infection. An acquired immune disease that has already cost the lives of millions of people is the HI virus. In all likelihood, the virus originated in African chimpanzees and was first transmitted to humans in the first half of the 20th century. It eventually became pandemic in the 1980s. Transmission most commonly occurs during blood transfusions, insertions of infected needles, and unprotected anal and vaginal intercourse. The virus is transmitted through the body fluids blood, semen, breast milk and vaginal secretions and enters the bloodstream of affected individuals through open wounds or mucous membranes. After infection, affected people suffer from flu-like symptoms. The actual disease often remains undetected for several years before the fatal AIDS disease breaks out. Another type of immune disease are the autoimmune diseases, which include allergies. In the case of an autoimmune disease, the organism fights the body’s own tissue because it is considered a foreign body. The exact origin of autoimmune diseases has not been conclusively clarified. However, a combination of a congenital and an acquired defect in the immune system is assumed. A well-known autoimmune disease is, for example, the inflammatory bowel disease Crohn’s disease, which occurs most frequently between the ages of 15 and 35. Sweden currently has the highest rate of new cases. The metabolic disease diabetes mellitus type 1 is also counted among the autoimmune diseases. Other diseases include chronic gastritis, the thyroid disease Hashimoto’s thyroiditis, narcolepsy, also known as sleeping sickness, rheumatoid arthritis and the widespread gluten intolerance celiac disease.
