Medical Genetics Nonspecific (Innate) Immunity This type of immunity is older phylogenetically, is present at birth, does not require a previous encounter with the offending substance, and does not develop memory. Innate immunity includes barriers such as the skin and chemical protection, such as gastric acidMedical Genetics Nonspecific (Innate) Immunity This type of immunity is older phylogenetically, is present at birth, does not require a previous encounter with the offending substance, and does not develop memory. Innate immunity includes barriers, such as the skin, and chemical protection, such as gastric acid