The Importance Of The Avian Immune System And Its Unique Features

The avian immune system is an invaluable model for studies on basic immunology and has provided a number of firsts. Graft versus host responses and the role of lymphocytes in adaptive immunity were first described using chick embryos and chickens. The bursa of Fabricius provided the first substantive evidence that bursal-derived lymphocytes (B cells) make antibodies. The development of the antibody repertoire by gene conversion was first identified in chickens and required the unique environment of the bursa. The avian major histocompatibility complex is minimal, compact, and some 20-fold smaller than that of mammals and, uniquely, is strongly associated with resistance to some diseases. The first attenuated vaccine was developed by Louis Pasteur against fowl cholera and the first vaccine against a naturally occurring cancer, Marek’s disease, was developed for chickens. Vaccination of chick embryos on the 18th day of incubation was another breakthrough providing protection early after hatching.