Immunology is a branch of medicine and biology that covers the medical study of immune systems in all organisms. In such we can see there is a difference of human immunology and comparative immunology in veterinary medicine and animal biosciences.

Immunology measures, uses charts and differentiate in context in medicine the studies of immunity on cell and molecular level, and the immune system as part of the physiological level as its functioning is of major importance. In the different states of both health, occurring symptoms and diseases; the functioning of the immune system and immunological responses such as autoimmune diseases, allergic hypersensitivities, or in some cases malfunctioning of immune system as for example in immunological disorders or in immune deficiency, and the specific transplant rejection)

Immunology has applications in numerous disciplines of medicine, particularly in the fields of rheumatology, virology, allergology (dermatology), bacteriology, oncology and further transplantation medicine.

The term was coined by Russian biologist Ilya Ilyich Mechnikov, who advanced studies on immunology and received the Nobel Prize for his work in 1908. He pinned small thorns into starfish larvae and noticed unusual cells surrounding the thorns. This was the active response of the body trying to maintain its integrity. It was Mechnikov who first observed the phenomenon of phagocytosis, in which the body defends itself against a foreign body.

Immunology has importance in reproductive medicine as the physical, chemical, and physiological characteristics of the components of the immune system in vitro, in situ, and in vivo.

In psychiatry it is said that psychiatric disorders lead to low levels of immunology but are not encountered any specific characteristics of immunological deficiencies.

Prior to the designation of immunity, from the etymological root immunis, which is Latin for 'exempt', early physicians characterized organs that would later be proven as essential components of the immune system. The important lymphoid organs of the immune system are the thymus, bone marrow, and chief lymphatic tissues such as spleen, tonsils, lymph vessels, lymph nodes, adenoids, and liver. However, many components of the immune system are cellular in nature, and not associated with specific organs, but rather embedded or circulating in various tissues located throughout the body.