All species have immune systems, which is studied in immunology, which is a discipline of biology and medicine that includes all of them. It is the study of immunological disorders (such as autoimmune diseases, hypersensitivities, immune deficiency, and transplant rejection) and the physical, chemical, and physiological characteristics of the immune system components in vitro, in situ, and in vivo that are charted, measured, and contextualised. Vaccines have uses in a wide range of medical disciplines, including organ transplantation, cancer treatment, rheumatology, virology, bacteriology, parasitology, psychiatry, and dermatology, among others.
Immunoglobulin was invented in 1908 by Russian scientist Ilya Ilyich Mechnikov, who improved immunological research and was awarded the Nobel Prize for his efforts. Mechnikov was the first person to use the name. He poked starfish larvae with little thorns until he observed peculiar cells around the thorns. He continued his research. As the body attempted to retain its integrity, this was the active reaction. A Mechnikov experiment was the first to detect the phenomena of phagocytosis, a process by which the body fights itself against an invading organism.
The term immunity was coined from the etymological root immunis, which means "exempt" in Latin. Early doctors used the term to describe organs that were subsequently discovered to be crucial components of the immune system. The thymus, bone marrow, and major lymphatic tissues such as the spleen, tonsils, lymph arteries, lymph nodes, adenoids, and liver are all essential lymphoid organs of the immune system. Thymuses and bone marrow are also important lymphoid organs. While many components of the immune system are biological in origin and not related with particular organs, many others are embedded or circulating in diverse tissues throughout the body, which makes them difficult to distinguish. Patients can have portions of their immune system organs surgically excised for examination while they are still alive if their health conditions deteriorate to the point where they are considered an emergency. These organs include the thymus, spleen, bone marrow, lymph nodes, and other lymphatic tissues.