Innate immunity provides a general immune response, meaning it is not specific to a particular pathogen; any foreign body or non-self molecule is a target.
The innate immune system includes physical barriers such as the skin and other epithelial surfaces that act as the first line of defense. However, when epithelial barriers are breached, other components of the innate immune response detect pathogens via germ line-encoded pattern recognition receptors, leading to a rapid immune response (within minutes to hours).
These pattern recognition receptors are often directed against cell surface and cell wall components of microorganisms, but bacterial DNA containing unmethylated CpG motifs also induce an innate immune response.
During hematopoiesis, the common myeloid progenitor (CMP) cell gives rise to the myeloid lineage which includes most of the component cells of the innate immune response.
CMP cells are a precursor to monocytes, which differentiate into macrophages and dendritic cells, and also cells of the granulocyte lineage, which includes mast cells, neutrophils, eosinophils and basophils. In contrast, cytotoxic natural killer (NK) cells are a component of the innate immune response derived from common lymphocyte progenitor (CLP) cells
Most cell types not specific to the immune system can harbor intrinsic innate immune functions in the form of cytoplasmic receptors and signaling and effector molecules. Signaling pathways active in the innate immune response include: