Macrophages
White blood cells that belong to the immune system and phagocytise foreign substances or substances labelled as such in the body, i.e. eat them up.
They are long-lived, mobile cells of the monocytic system that originate from blood monocytes and together with local macrophages (tissue macrophages) form the mononuclear phagocyte system (reticulohistiocytic system).
As antigen-presenting cells, macrophages have a key function in the humoral immune response. They're richly endowed with Lysosomes. They adhere to surfaces with electrical charge, form pseudopodia and are capable of phagocytosis, pinocytosis, storage of small foreign bodies and cell debris, stimulation of proliferation and differentiation of B-lymphocytes to plasma cells.
During an infection they migrate to the infection site and differentiate (change to a more specific cell shape) under the influence of cytokines and antigens to macrophages in the tissue. A distinction is made between mobile macrophages that migrate from the blood as needed and local tissue macrophages, which make up the majority of the macrophage population and are called dendritic cells.