Chapter 5 - Cell Recognition and the Immune System Flashcards
What is the name of molecules which identifies each cell?
Antigens
What are pathogens?
Pathogens are the first line of defence in the immune system, and are able to hydrolyse any cell with different antigens to its organism
How does phagocytosis work?
The phagocyte uses membrane receptors to track down pathogens from its released waste products. Once it reaches the cell it binds onto it and engulfs it, forming a phagosome. Lysosomes then fuse with the phagosome releasing lysozymes which hydrolyse the pathogen
What is a pathogen?
A pathogen is any cell or virus which can cause harm or disease in living organisms
What response do phagocytes cause after hydrolysing pathogens and how?
Once a pathogen is hydrolysed, the phagocyte places its antigens on its cell surface becoming an antigen presenting cell. It will then go through the entire body until it finds a T cell with a complementary receptor, and the bonding of the phagocyte activates the T cell
What does a T cell do once activated?
It can become cytotoxic (or a “Killer T cell”) go to the area where pathogens are and attract more phagocytes (helper T cells) or seek out a B cell with the same antigen as the T cell to activate the humoral response
What is the humoral response?
When the activated T cell finally reaches the same B cell it activates it, causing clonal proliferation of plasma cells. The plasma cells then begin to produce and secrete large amount of antibodies specific to the invading pathogen, which can work in a variety of ways
How can antibodies function?
Antibodies can function in several different ways. One of the most common is agglutination, where the antibodies are able to “stick” several different pathogens together so that they can all be engulfed by phagocytes at once. They can also bind to the invading pathogen and send out a chemical marker to phagocytes
What is the structure of an antibody
Antibodies are made up of two “heavy chains” of polypeptides along the inside , and then two “light chain” polypeptides at the end of each of the heavy chains. The base of the heavy chains is the constant region, which binds to receptors in cells such as B cells, whereas the variable region found at the end of the heavy and light chain is what binds to specific antigens to form an antibody-antigen complex. They may also act as antitoxins
How are humans protected from successive infections from the same pathogen?
Once a pathogen has been successfully removed from the body, many of the T and B cells die however a small amount become memory T cells and B cells and line up in the spinal column, which is one of the first places antigen presenting cells go to stimulate a humoral and cellular response, meaning the response is stimulated much more quickly than the first time
What are vaccines?
Vaccines are an injection of antigens from a pathogen or a weakened or dead form of the pathogen, usually combined with a natural irritant such as aluminium to illicit a immune response. Vaccines allows the body to fight a version of the pathogen and learn its antigen shape and form memory cells without the danger that the pathogen poses when alive and functional, meaning it is much safer than the body naturally fighting the pathogen and forming memory cells that way
What is the idea behind herd immunity?
Herd immunity is the idea that when enough people in a population have a vaccine against a specific disease (e.g. polio), then the people who are medically unsafe or incapable of receiving the vaccine still benefit from the protection afforded by vaccines because the vaccinated people will kill any pathogens before they are able to be spread and infect unvaccinated people
What is the difference between active and passive immunity?
Active immunity is aquired, lasting immunity to a disease. It can be natural or artificial, with artificial being aquired from vaccines. Passive immunity however is immediate immunity aquired from being given monoclonal antibodies. It is not lasting because the body cannot produce those antibodies again once they break down, such as snake antivenom
How do HIV viruses infect healthy human cells?
Once the HIV is in the bloodstream, it will attach to the proteins on the outside of the helper T cells (usually), and use its enzymes to insert its RNA. Once inside the cell, the RNA is converted into DNA using the reverse transcriptase from the virus. This DNA is then integrated into the hosts DNA and turned into proteins like normal, forming new HIV viruses
How does HIV lead to AIDS?
AIDS is aquired immunodeficiency syndrome, because HIV targets helper T cells and therefore kills them in the process, the number of them present in the blood is reduced. This makes humans more susceptible to other diseases, such as pnuemonia, which eventually kills them instead
