Mononuclear Phagocyte Cells

(2). Mononuclear phagocyte cells (i) Macrophages as mononuclear phagocytes Macrophages are themacrophages most important professional phagocytes. As professional phagocytes, have a dual role in organizing the immune response. These cells are produced in the bone marrow and myeloid stem cells through the promonocyte stage.and Cellswhen thatthey are not yetthefullycirculation developed then enter the bloodstream as monocytes leave and arrive inand the tissue they inundergo various additional changes and become mature cells then settle the tissue as macrophages. These cells are found, among others, in the lungs as alveolar macrophages, in the liver as Kupffer cells, lining the sinusoids of the spleen and lymph nodes, as mesangial cells in the glomerulus, microglial cells in the brain and osteoclast cells in the bones. Some ofofthem differentiate into other cells,months for example dendritic cells. The lifespan macrophages can reach several or even years, so their lifespan is much longer than polymorphonuclear (P) cells which only live for 2-3 days. Apart from that, their function in the immune system is also different.Macrophages have an important role in theare: immune response. The main functions of macrophages in innate immunity 1). Macrophages phagocytose foreignand particles suchorastissues microorganisms, macromolecules including antigens even cells damaged or dead, for example erythrocytes that are no longerthemselves viable. that are 2). Thepresence recognition of macrophages against foreign substances is made possible by the of receptors for phospholipids, while their function as effector cells, namely destroying microorganisms as wellother as malignant cellsa number and foreign objects, is possible because these cells, among things, have of lysosomes in the cytoplasm which contain hydrolases and peroxidases which are destructive enzymes. . Apart from that, macrophages alsoforhave receptors for thepresence Fc fragment IgGi and IgG3 as well as IgE, and receptors complement. The of these receptors increases the ability ofThus thesemacrophages cells to destroyareforeign objectscells” coated with antibodies or complement. “scavenger major in the body. Macrophages also express MHC classareIIactivated. on their surface, and MHC II expression increases when macrophages This is important because apart fromwhich beingthey effector cells, macrophages also II. function to present antigens to T cells do by expressing MHC class Apart from having receptors for various types of lymphokines, for example receptors for migration inhibitory factorrecruit (MIF)other and IFN-y, macrophages also produce a numberand of are cytokines that inflammatory cells, especially neutrophils, responsible forproduced various systemic effects of(IL-1) inflammation such astofever. Among the cytokines are interleukin-1 which is needed stimulate T and B cell proliferation, fibroblast growth factor and vascular endothelium which are needed to repair damaged tissue. Phagocytic cellsaidhave receptors for immunoglobulins and process. for complement components, which in contact and in initiating the digestive The receptor is called toll like receptor (TLR). There are 11 types of toll like receptors. Each of the 11 different Toll-like receptors recognizes different pathogen products. Some examples arepeptidoglycan shown here. TLR1 recognizes lipoproteins found inTLR4 mycobacteria, TLR2 binds found in gram-positive bacteria, identifies lipopolysaccharides found in gram-negative bacteria. TLR binding to antigens is enhanced by the presence of opsonins, a term derived from the that Greekattach wordtomeaning "to prepareand for food." Opsonins are serum Cproteins foreign substances help prepare for phagocytosis. reactive protein, complement components, andsurface antibodies are on all foreign important opsonins. Opsonins can act by neutralizing the charge particles, making it easier for cells to approach each other. (ii). Monocytes as mononuclear phagocytes Monocytes are "wondering" mononuclear phagocytes that always circulate in the bloodstream. The characteristics, stem cells and biological activities and killing mechanisms of monocytes are no different from macrophages. Mechanism of killing by mononuclear phagocytes : After attachment occurs between the macrophage/monocyte and the antigen particle, the cell cytoplasm flows around the particle and annexation occurs. Increased oxygen consumption, known as "oxidative burst" or oxidation burst, occurs in the cell along with the activity of pseudopodia covering antigen particles enteringgradually the vacuole. Thetowards structure formed is known asNext, the phagosome. The phagosome moves the center of the cell. contact occurs between the phagosome and the cytoplasmic granules, and ends with fusion between the cytoplasmic granules and the phagosome, resulting in the formation of a phagolysosome. The cytoplasmic granules then release their contents, and digestion occurs. Any ingested material is removedisfrom the cell by exocytosis. The process of "killing" or killing microorganisms actually very dependent on oxygen. Cell which (iii). Polymorphonuclear cells (PMN) Polymorphonuclear cells (PMN) originate from myeloid stemthese cells,cells andcan constitute 60-70% of the leukocytes in circulating blood, although also be found extravascularly. PMN cells have an3 types nucleus which is divided into several lobules, and in the cytoplasm there are of granules, namely primary, secondary and tertiary granules.lysozyme Primaryand granules are azurophilic granules that contain myeloperoxidase, a number of positively charged (cationic) proteins. Secondary granules contain lactoferrin, lysozyme and B-12 binding protein, while tertiary granules contain lysozome and acidand hydrolase. Mi granules are very important in the process of killing bacteria other immunological reactions. Neutrophils 90% ofiscirculating granulocytes consisttissue of neutrophils. Its lifetime inNeutrophils the Nearly bloodstream about 4-8 hours but in cellular it can live longer. react quickly to stimuli, can move towards areas of inflammation because they are stimulated by chemotactic factors which include, among others, released by complement or activated lymphocytes. Like macrophages, the main function of neutrophils iskilling to provide a nonspecific immune response by carrying out phagocytosis and or eliminating incoming microorganisms. Mi function is supported and enhanced by complement or antibodies, and toasbind complement and antibodies neutrophils have receptors for Fc-IgG as well receptors for C3b and C3d. Neutrophils have granules containing destructive enzymes and various proteins which, apart from being able to damage microorganisms, can also trigger an inflammatory reaction when released.'