Monocytes and Macrophages
Monocytes and macrophages are critical effector cells that serve to regulate inflammation and the innate immune response. Monocytes originate in the bone marrow (an early mouse marker is Ly-6G), and are prevalent in the blood, bone marrow, and spleen where they act as immune effector cells. Activation of these cells occurs through the up regulation of markers including CD11b and CD62L. Once activated, monocytes produce various inflammatory cytokines that facilitate the subsequent removal of cells and toxic molecules. Monocytes may differentiate into dendritic cells or macrophages during inflammation, acting as resident phagocytic cells in lymphoid and non-lymphoid tissues. Utilizing pathogen-recognizing receptors such as TLR2 and TLR4, macrophages are efficient immune effectors that can contribute to both innate and adaptive immune processes, providing phagocytosis and inducing production of inflammatory cytokines.