Innate Immune System Definition

noun

The component of the immune system in animals that is genetically determined and is nonspecific, as distinguished from the adaptive immune system. Elements of the system include mucous secretions, complement proteins, and certain white blood cells, especially neutrophils, macrophages, and dendritic cells.

American Heritage

(immunology) This is the initial line of defense that entails a cascade of cells and mechanisms that protect the host from infection by different organisms in an indeterminate pattern.

Wiktionary