Innate immunity is a type of nonspecific defense that is present at birth. This immunity is achieved by erecting various types of barriers against the entry of external factorsn our body. There are four types of barriers in innate immunity. Like :
(1) Physiological barrier : In the stomach Acid, saliva in the mouth, tears in the eyes, all these prevent bacterial growth.
(2) Physical Barrier : Skin is the main barrier on our body which prevents the entry of microorganisms. The mucus coating of the epithelium lining the respiratory, gastrointestinal and genitourinary tracts also helps prevent pathogens from entering the body.
(3) Cellular barrier : In the blood of our body, some types of leukocytes like polymorphonuclear leukocytes (PMNL, neutrophils) and monocytes (monocytes) and natural, killer lymphocytes and Macrophages in tissues. (Macrophages) eat and destroy germs.
(4) Cytokine resistance : Virus-infected cells secrete proteins called interferons which protect uninfected cells from further viral infection.