After a pulp exposure, pulp cells are recruited, then differentiate into odontoblast-like cells, and contribute to the formation of a dentine bridge and thus increasing the residual dentin thickness. Odontoblast-like cell is a mineralized structure formed by a new population of pulp-derived which can be expressed as Toll-like receptors. They are responsible for the upregulation of innate immunity effectors, including antimicrobial agents and chemokines. One important antimicrobial agent produced by odontoblast is beta-defensins (BDs). BDs kill microorganisms by forming micropores that destroy membrane integrity and cause leakage of the cell content. Another one is nitric oxide (NO), a highly diffusible free radical, which stimulates the production of chemokine to attract immune cells into the affected areas and neutralize bacterial by-product in human pulp cells in vitro.