Which type of immunity is characterized by natural defenses?

Innate immunity is characterized by natural defenses, which are the body's first line of defense against pathogens. This type of immunity functions in a nonspecific manner, meaning it responds to all pathogens in a similar way without requiring prior exposure to them. The innate immune system includes physical barriers such as skin and mucous membranes, as well as various immune cells like macrophages and neutrophils that act quickly to identify and destroy invading microorganisms.

This natural defense mechanism is crucial because it provides immediate protection until the more specific adaptive immune response can take over. The body does not need to "learn" how to respond to an invader because these defenses are already in place at birth. Other types of immunity, such as adaptive immunity, involve a more complex and slower response to specific pathogens based on previous exposures, which does not apply to innate immunity.