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Microglia also differ from macrophages in that they are much more tightly regulated spatially and temporally in order to maintain a precise immune response. [18] Another difference between microglia and other cells that differentiate from myeloid progenitor cells is the turnover rate.
Macrophages are found in essentially all tissues, [4] where they patrol for potential pathogens by amoeboid movement. They take various forms (with various names) throughout the body (e.g., histiocytes, Kupffer cells, alveolar macrophages, microglia, and others), but all are part of the mononuclear phagocyte system.
Macrophages are diffusely scattered in the connective tissue and in liver (Kupffer cells), spleen and lymph nodes (sinus histiocytes), lungs (alveolar macrophages), and central nervous system (microglia). The half-life of blood monocytes is about 1 day, whereas the life span of tissue macrophages is several months or years.
Tumor-associated macrophages/microglia are the main infiltrate in gliomas, comprising up to 40% of the tumor mass. [22] TAMs are either of peripheral origin (macrophages) or representing brain-intrinsic, yolk sac -derived microglia , that create a supportive stroma for neoplastic cell expansion and invasion. [ 21 ]
However, cellular extensions, in general, can be found on a larger "macro" scale, occupying relatively large areas of the cell membrane. [1] For example, microglia can use their primary processes to constantly monitor and evaluate alterations in the brain environment, and they can further deploy thin filopodia from these primary processes to ...
The exception is microglia, which are derived from hematopoietic stem cells. In the adult, microglia are largely a self-renewing population and are distinct from macrophages and monocytes, which infiltrate an injured and diseased CNS. In the central nervous system, glia develop from the ventricular zone of the neural tube.
Macrophages are found throughout the body in almost all tissues and organs (e.g., microglial cells in the brain and alveolar macrophages in the lungs), where they silently lie in wait. A macrophage's location can determine its size and appearance. Macrophages cause inflammation through the production of interleukin-1, interleukin-6, and TNF ...
Monoblasts are normally found in bone marrow and do not appear in the normal peripheral blood. [3] They mature into monocytes which, in turn, develop into macrophages . [ 4 ] They then are seen as macrophages in the normal peripheral blood and many different tissues of the body.