innate immunity

Immunity that is present at birth and lasts a person’s entire life. Innate immunity is the first response of the body’s immune system to a harmful foreign substance. When foreign substances, such as bacteria or viruses, enter the body, certain cells in the immune system can quickly respond and try to destroy them. Innate immunity also includes barriers, such as skin, mucous membranes, tears, and stomach acid, that help keep harmful substances from entering the body.