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[41] [43] Therefore, macrophages interact mostly with previously activated T helper cells that have left the lymph node and arrived at the site of infection or with tissue resident memory T cells. [42] Macrophages supply both signals required for T helper cell activation: 1) Macrophages present antigen peptide-bound MHC class II molecule to be ...
Macrophages are produced through the differentiation of monocytes, and after ingestion of bacteria, secrete enzymes to destroy the ingested particle. These cells reside in every tissue of the body, and upon infected tissue, are recruited to the tissue. Once recruited, macrophages will differentiate into specific tissue macrophages.
During the years that followed after Aschoff had originated the concept of RES, research on macrophages and their role as phagocytes steadily increased, and in 1960 the concept of the mononuclear phagocyte system was proposed to denote all cells identified as macrophages. The cells of MPS, by way of their common functional signature as ...
Giant cells are also known to develop when infections are present. They were first observed as early as the middle of the last century, but it is not fully understood why these reactions occur. In the process of giant cell formation, monocytes or macrophages fuse together, which could cause multiple problems for the immune system. [citation needed]
In general, monocytes and their macrophage and dendritic cell progeny serve three main functions in the immune system. These are phagocytosis , antigen presentation, and cytokine production. Phagocytosis is the process of uptake of microbes and particles followed by digestion and destruction of this material.
Antigen presentation is a process in which some phagocytes move parts of engulfed materials back to the surface of their cells and "present" them to other cells of the immune system. [57] There are two "professional" antigen-presenting cells: macrophages and dendritic cells. [58]
Macrophage polarization is a process by which macrophages adopt different functional programs in response to the signals from their microenvironment. This ability is connected to their multiple roles in the organism: they are powerful effector cells of the innate immune system, but also important in removal of cellular debris, embryonic development and tissue repair.
Kupffer cells, also known as stellate macrophages and Kupffer–Browicz cells, are specialized cells localized in the liver within the lumen of the liver sinusoids and are adhesive to their endothelial cells which make up the blood vessel walls. Kupffer cells comprise the largest population of tissue-resident macrophages in the body.