The inducible defenses are a function of the immunological system and the immune responses . The constitutive defenses are innate and immediately available for host defense. The inducible defenses must be triggered in a host and initially take time to develop. The type of resistance thus developed in the host is called acquired immunity . The term immune usually means the ability to resist infectious disease.
Immunity refers to the relative state of resistance of the host to a specific pathogen.
Acquired immunity, itself, is sometimes divided into two types based on how it is acquired by the host. Active immunity can persist a long time in the host, up to many years in humans. Passive immunity is typically short-lived and usually persists only a few weeks or months. Bacteria are composed of various macromolecular components that are antigenic to their host and bacterial antigens interact with the host immunological system in a variety of ways. Furthermore, the interaction between these immune tissues and intestinal bacteria results in the production of serum and secretory antibodies that are directed against bacterial antigens.