What Is Opsonization?

PrintPrintEmailEmailSaveSave
Image Credit: 
profelis.org
Main Image: 
Process of opsonization

Anitbody Opsonization is the process by which a pathogen (virus, fungi or bacteria that causes disease) is marked of ingestion and destruction by a phagocyte (white blood cells that protects the body by ingesting harmful foreign particles). Opsonization involves the binding of an opsonin i.e., antibody, to a receptor on the pathogen’s cell membrane. Antibodies are proteins that exist in bodily fluids and are used both as a detection and response device by the immune system. After opsonin binds to the membrane, phagocytes are attracted to the pathogen. So, Opsonization is a process in which pathogens are coated with a substance called an opsonin, marking the pathogen out for destruction by the immune system.

What is Phagocytosis?

The process of killing and ingesting a pathogen is called “phagocytosis”. Phagocytes ingest the pathogens and then kill them by exposing them to toxic chemicals. The chemicals are stored in small membrane-bound parcels within the phagocytes, and these parcels are activated to open when a phagocyte ingests a pathogen.

 

What is Antibody-dependent Cellular Cytotoxicity?

Opsonization also lead to pathogen death in a second mechanism known as “Antibody-dependent Cellular Cytotoxicity”, in which immune cells directly kill pathogens without ingesting them. Antibodies are proteins that exist in bodily fluids and are used both as a detection and response device by the immune system. During this process, antibodies act as opsonins and then activate immune cells called ‘granulocytes’. Granulocytes are a type of lymphocyte, or white blood You do not have access to view this node. These cells are part of immune system, and are involved in several different types of immune reaction. Granulocytes then release toxic chemicals into the environment around the pathogens to destroy them. In addition to killing pathogens, this procedure also causes tissue damage through inflammation.

 

Why is Opsonization important?

Opsonization of pathogens such as bacteria and viruses are important because both immune cells and pathogen cells are negatively charged. This means it is not easy for a cell to move close enough to a pathogen to begin ingestion or straight killing. The evolution of opsonization solves this issue since they have receptors which identify and bind to protein molecules on immune cells. So, when a pathogen has been covered in opsonins, the receptors on the opsonins can bind immune You do not have access to view this node, bringing cells in close proximity to the pathogens to facilitate ingestion or straight killing.

 

What are the substances that act as opsonins?

There are various substances that perform as opsonins: all of these are proteins which are active in immune system. The two antibody types known as IgG and IgA are both opsonins.

  • IgG: This is active in blood and You do not have access to view this node.
  • IgA: This is energetic in mucosal surfaces such as the airways, urogenital system, and gut.

Many proteins that act in the complement system are also opsonins. The complement system is a cascade of reactions between numbers of different proteins. The final result of the cascade is opsonization of pathogens as well as direct pathogen killing through the formation of a protein complex which penetrates the hole in bacterial cell wall.

 

Which causes defects in Opsonization?

Several types of inherited genetic diseases can cause defects in opsonization. For example,

  • Those people with diseases which cause deficiencies in the complement system are more prone to infections, mainly bacterial infections.
  • Diseases which affect B lymphocytes (white blood You do not have access to view this node), the cells which produce antibodies, also are prone to infection to a greater extent.

Individuals with these immune deficiencies have different levels of risk to serious and even deadly infections with pathogens which would not cause diseases in healthy people.

External References
Related Videos: 
See video