In a non-infected pulp, leukocytes are present to sample biologically and respond to the surrounding environment, including macrophages, dendritic cells (DCs), T cells and B cells. This sampling process is part of the normal protective immune response as it triggers leukocytes from the circulatory system to adhere to endothelial cells lining blood vessels and then migrate to the site of infection for defense potential. Macrophages can phagocytose bacteria and activate T cells triggering an adaptive immune response which occurs in association with DCs. In the pulp, DCs secrete a range of cytokines that influence both innate and adaptive immune responses, and they are considered key regulators of the tissue’s defense against infection. There is also a comparatively small number of B cells present in the healthy pulp tissue, and as there is pulpitis and caries progression, their numbers also increase.