Immunity (from the Latin. Immunitas — «liberation») — congenital or acquired protection of a living organism from infections and pathogens. It is provided by the reaction of the immune system to foreign objects and their destruction (immune response).
The organs of the immune system include the bone marrow, thymus (also the thymus gland), spleen and lymph nodes. In the thymus gland from the bone marrow, the prehytocytes enter, from which T-lymphocytes (T-cells) are subsequently formed. T cells are involved in the immune response. T-helpers, for example, activate T-killers, which, in turn, kill the damaged cells of their own body. In addition to them, B-lymphocytes, NK-cells, neutrophils, basophils and eosinophils take part in the defense of the body. There are also monocytes that capture and absorb bacteria, dead cells and toxins.
Inflammatory processes that accompany the fight of immune cells with pests can occur in all organs and tissues, except the brain, eyes, testicles and placenta. This feature is called the immune privilege and is due to the fact that the reaction of the immune system to antigens in these organs can cause a loss of their functions.
Immune system disorders cause various diseases, including cancer and immune deficiency. The production of large amounts of antibodies by the body can also lead to negative consequences: killer cells begin to fight healthy cells, as a result of which normal tissues are destroyed. In this case, the person suffers from autoimmune diseases, such as hypersensitivity (allergies) or rheumatism.
The study of immune reactions involved in immunology. In the 11th century, the Persian scientist Avicenna advanced the theory of acquired immunity. In 1546, this theory was developed by the Italian doctor Girolamo Fracastoro. In the 18th century, the first vaccines against smallpox, diseases, the epidemic of which claimed, presumably, millions of lives in Europe, China, Japan, Korea and the Middle East, appeared. Later, vaccines against some other diseases were produced. For example, in 1881, Louis Pasteur tested the rabies vaccine. For achievements in the study of immunity, many scientists received the Nobel Prize. The last award in this field was awarded to Ralph Steinmann, Jules Hoffman and Bruce Botler in 2011.