Immunology is a broad branch of
biomedical science that covers the study of all aspects of the
immune system in all
organisms. It deals with, among other things, the
physiological functioning of the immune system in states of both health and disease; malfunctions of the immune system in immunological disorders (
autoimmune diseases,
hypersensitivities,
immune deficiency,
transplant rejection); the physical, chemical and physiological characteristics of the components of the immune system
in vitro,
in situ, and
in vivo. Immunology has applications in several disciplines of science, and as such is further divided.