A scavenger cell is a cell of the immune system that is specialized for the engulfment and dislocation of bacteriums, foreign atoms and other pathogens in the blood stream ; such as a neutrophil, macrophage or dendritic cell. In this essay I am traveling to depict how a macrophage would phagocytose a pathogen.
A monocyte is the largest cell in the organic structure and it is a precursor to macrophages in the tissue. Initially the cells are derived from the bone marrow of promonocytes, these so differentiate to go go arounding blood monocytes, which so emigrate down the blood watercourse and settle in the tissues as mature macrophages ( Roitt & A ; Delves, 2001 ) .Macrophages are really big and long lived cells, found in most connective tissue around the cellar membrane of little blood vass, where their chief function is to filtrate off foreign stuffs. Their forte is contending off bacteriums, viruses and Protozoa that are capable of life within the host. They are peculiarly concentrated in the lung ( alveolar macrophages ) , liver ( Kupffer cells ) , the liner of the lien and lymph nodes ( sinus histiocytes ) and cardinal nervous system ( microglial cells ) . These constitute the mononuclear scavenger cell system ( Kumar, Abbas, Fausto, & A ; Mitchell, 2007 ) .
Phagocytosis
Phagocytosis is a critical procedure in the immune system where the engulfment and dislocation of infective agents and aging cells by scavenger cells such as macrophages occurs. It is besides necessary for tissue remodelling and fix. Its complexnesss are due to the diverse figure of receptors that are capable of exciting phagocytosis where most atoms are recognised by more than one receptor. The acknowledgment mechanism before phagocytosis can either occur cellularly or humorally ( Aderem & A ; Underhill, 1999 ) . There are three chief stairss that occur for the successful phagocytosis of pathogens.
Attachment of pathogen to phagocyte
Engulfment
Killing and debasement of pathogen
Attachment of pathogen to phagocyte:
Phagocytes are attracted to the country of invasion due to chemical merchandises of the bug such as phospholipids released by injured mammalian cells or by constituents of the complement system. Innate unsusceptibility does non recognize every individual antigen but it does non necessitate to as pathogens have molecular constructions that are shared by many other similar pathogens. These molecules are called Pathogen Associated Molecular Patterns ( PAMPs ) , and are usually polyoses or polynucleotides that are non found on the host ; illustrations are LPS from e-coli. The receptors that recognise these common PAMPs are called pattern acknowledgment receptors ( PRRs ) ( see figure 1 ) and are at that place so as to trip an immediate response against the invading bug. An illustration of a PRR is the mannose receptor which binds to the polyose Mannose.
The bugs undergo a procedure called opsonization, where they are coated with molecules that alter the construction of the bacteriums in order to do them more susceptible to the action of scavenger cells, these molecules such as antibody molecules immunoglobulin G ( IgG ) , complement proteins C3b, Mannose adhering Lectin. For illustration if a bug is opsonised by the antibody IgG. The Fab part of the IgG will adhere to the antigenic determinant of the bug, go forthing the Fc part free to adhere to the Fc receptor for IgG ( called FcIA?RI ) on the macrophage ( see figure 1 ) ; therefore adhering the pathogen to the macrophage ( Kumar, Abbas, Fausto, & A ; Mitchell, 2007 ) .
Engulfment:
When the opsonised atom has bound to its specific receptor on the surface of the scavenger cell it causes it to undergo a rearrangement in the actin cytoskeleton via polymerisation of the actin at the site of consumption triping engulfment of the bug via an actin-based mechanism. Binding induces the actin fibrils of the phagocytic cell to direct out pseudopods that extend around the bug and a phagocytic vacuole signifiers ; known as a phagosome ( Aderem & A ; Underhill, 1999 ) .
Killing/degradation:
The cytol of the macrophage contains cysts called lysososmes produced by the Golgi setup incorporating digestive enzymes, microbicidal substances and toxic O group. The membrane of the lysosome fuses with the membrane of the phagosome, and dispatch its granule content, organizing a phagolysosome ( Janeway, Travers, Mark, & A ; Mark, 2001 ) .
There are two killing systems in phagocytosis:
Oxygen dependant system
Oxygen independent system
Oxygen dependent system:
The membrane of the scavenger cell contains enzyme oxidase that converts O to a superoxide anionAA ( O2- ) , this anion combines with H2O to organize H peroxide and hydrated oxide groups which are reactive O species ( ROS ) which destroy bugs. In macrophages Nitric Oxide ( NO ) can unite with Hydrogen Peroxide to organize peroxynitrite groups. Macrophages besides secrete out inflammatory cytokines such as Interleukin 1 ( IL-1 ) which promote inflammatory response ( Roitt & A ; Delves, 2001 ) .
Oxidase besides acts as an negatron pump that pumps in protons ( H+ ) inside the phagosome, this in bend reduces the pH within the phagosome and so when the phagolysosome forms the pH is right for acerb hydrolases to interrupt down cellular protein.
Oxygen Independent system:
The granules of the lysosome contain several components that allow them to kill infective pathogens, for illustration, lysozyme an enzyme that breaks down the bacterial coat of oligosaccharides, defensins which are peptides that alter the cytoplasmatic membrane by bring forthing holes therefore killing bugs and other any digestive enzymes that break down proteins, RNA, phosphate compounds, lipoids, and saccharides. These all selectively exposes the ingested bug and causes it to degrade and destruct ( Kumar, Abbas, Fausto, & A ; Mitchell, 2007 ) . The digestive contents of the phagolysosome are so eliminated from the scavenger cell by a procedure of exocytosis.
In decision, phagocytosis is a critical procedure in the immune system that require scavenger cells such as macrophages which are long lived cells whose chief function is to filtrate off pathogens such as bacteriums. There are three chief stairss to for this to happen. First the pathogen has to undergo opsonization in order to be recognised and attach to the specific receptor on the macrophage. Second the scavenger cell is engulfed by the macrophage organizing a phagosome. Then it fuses with cytoplasmatic lysosome organizing a phagolysosome, where killing and debasement of the ingested stuff occurs as a consequence of the lysosome granules.
