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Macrophages can be protective in different ways: they can remove dead tumor cells (in a process called phagocytosis) following treatments that kill these cells; they can serve as drug depots for some anticancer drugs; [106] they can also be activated by some therapies to promote antitumor immunity. [107]
Phagocytosis (from Ancient Greek φαγεῖν (phagein) 'to eat' and κύτος (kytos) 'cell') is the process by which a cell uses its plasma membrane to engulf a large particle (≥ 0.5 μm), giving rise to an internal compartment called the phagosome. It is one type of endocytosis. A cell that performs phagocytosis is called a phagocyte.
[49] [50] These molecules mark the cell for phagocytosis by cells that possess the appropriate receptors, such as macrophages. [51] The removal of dying cells by phagocytes occurs in an orderly manner without eliciting an inflammatory response and is an important function of phagocytes. [52]
The cells are primarily monocytes and macrophages, and they accumulate in lymph nodes and the spleen. The Kupffer cells of the liver and tissue histiocytes are also part of the MPS. The mononuclear phagocyte system and the monocyte macrophage system refer to two different entities, often mistakenly understood as one. [citation needed]
One type of MHC class II deficiency, also called bare lymphocyte syndrome, is due to mutations in the genes that code for transcription factors that regulate the expression of the MHC class II genes. [16] It results in the depletion of CD4 T cells and some immunoglobulin isotypes even though there are normal levels of both CD8 Cells and B cells ...
Phagocytosis of a bacterium, showing the formation of phagosome and phagolysosome. In cell biology, a phagosome is a vesicle formed around a particle engulfed by a phagocyte via phagocytosis. Professional phagocytes include macrophages, neutrophils, and dendritic cells (DCs). [1]
Opsonins induce phagocytosis of targets by binding the targets (e.g. bacteria) and then also binding phagocytic receptors on phagocytes. Thus, opsonins act as bridging molecules between the target and the phagocyte, bringing them into contact, and then usually activating the phagocytic receptor to induce engulfment of the target by the phagocyte.
Step 1: A macrophage engulfs the pathogen. Step 2: The macrophage then digests the bacterium and presents the pathogen's antigens. Step 3: A T helper cell binds to the macrophage and becomes an activated T helper cell. Step 4: The activated T helper cell binds to a B cell in order to activate the B cell.