Immunology is a branch of life science that covers the study of all aspects of the system altogether in organisms. It deals with the physiological functioning of the system in states of each health and diseases; malfunctions of the system in immunologic disorders (autoimmune diseases, hypersensitivities, immune deficiency, transplant rejection); the physical, chemical and physiological characteristics of the elements of the system in vitro, in situ, and in vivo. Medicine has applications in many disciplines of science. Even before the idea of immunity was developed, various early physicians characterized organs that will later persuaded as part of the system. The key bodily fluid organs of the system area unit the thymus and bone marrow, and secondary body fluid tissues like spleen, tonsils, humour vessels, humour nodes, adenoids, and skin and liver. once health conditions warrant, system organs together with the thymus, spleen, parts of bone marrow, humour nodes and secondary body fluid tissues are often surgically excised for examination whereas patients area unit still alive. Many elements of the system are literally cellular in nature and not related to any specific organ however rather area unit embedded or current in varied tissues placed throughout the body. The science of medicine encompasses the study of the event, anatomy functions and malfunctions of the system, all of that area unit of elementary importance to the understanding of sickness among the human. The system is formed from many sorts of molecules and cells that are unit distributed in each tissue of the body, further as specialized bodily fluid organs that act during a coordinated manner to stop or eliminate microorganism infections, to suppress the expansion of tumors, and to initiate repair of broken tissues. The system commonly acknowledges and responds to foreign molecules or broken self, however not healthy host cells and tissues. The innate system maintains barriers to microorganism invasion and provides vital organic chemistry and cellular responders to infections that area unit fully essential for the survival when affected by abundant microbes.