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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 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.
The activation of T H 1 and M1 macrophage is a positive feedback loop, with IFN-γ from T H 1 cells upregulating CD40 expression on macrophages; the interaction between CD40 on the macrophages and CD40L on T cells activate macrophages to secrete IL-12; and IL-12 promotes more IFN-γ secretion from T H 1 cells.
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.
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 ]
The difference between foot processes, and lamellipodia, which are broad sheet-like protrusions, and filopodia, which are long slender pointed extensions, is that lamellipodia and filopodia are especially significant for cell movement and migration, and they are "macro" membrane protrusions.
Specific deletion of FIRE prevents differentiation of only specific macrophage types such as brain microglia and macrophages in the skin, kidney, heart, and peritoneum whereas deletion of the entire mouse Csf1r gene widely prevents macrophage differentiation, causing profound developmental defects. [8]
The monoblast is the first stage of monocyte-macrophage maturation. The developmental stages of the monoblast are: CFU-GM (pluripotential hemopoietic stem cell or hemocytoblast) -> monoblast -> promonocyte-> monocyte-> macrophage/dendritic cell. During their development, monocytes are present in large packs in all of the lymph nodes in the body ...