Specific Immune System 12.6 Flashcards
Antigens
These are molecules that exist on the cell surface of all cells, whether they are self antigens or non-self antigens which means they belong to something foreign. They trigger an immune response which means antibodies which are polypeptides are produced.
Specific Immune System
This is a lot slower than the non-specific system and can take up to 14 days to take affect. However if there is a second invasion of the same pathogen, the response will be a lot faster.
What are antibodies?
These are y shaped glycoproteins called immunoglobulins. They bind to antigens on a pathogen that has triggered the immune response and there’s a specific antibody for each type of antigen, they aren’t all the same.
Structure of antibodies
They are made up of 2 long polypeptide chains called heavy chains and 2 shorter chains called light chains. the heavy and light chains are bonded together with disulphide bridges and they are also in the chains structure to make it more solid. They also have antigen binding sites on each side of the antibody. They also have hinge regions on the antibody where each heavy chain angles off into the y shape and this makes it more flexible and allows it to bind to two antigens at the same time.
How can antibodies bind to antigens?
They have antibody binding sites which is an area on the variable region which is 110 amino acids on the heavy and light chain on both sides of the antibody. Each antibody will have it’s own specific variable region that can be different shapes and will bind to the antigens in a lock and key mechanism in the same way as enzymes and substrates. When they bind they form antigen-antibody complex. The rest of the antibody is called the constant region which is the same for all antibodies. This also has a receptor binding site for when it joins to cells.
How do antibodies defend the body?
- They act as opsonins so it’s easier for a phagocyte to engulf an antigen-antibody complex.
- Once in an antigen-antibody complex, the pathogen cannot enter the host cell and cause any more damage
- They act as agglutinins which causes pathogens carrying antigen-antibody complexes to clump together so they cannot move around the body and also to make it easy for the phagocyte to engulf many pathogens at the same time.
- They can act as anti-toxins and make the toxins produced by pathogens harmless.
Lymphocytes
The immune system is based on these white blood cells called lymphocytes. There are both B and T lymphocytes. B lymphocytes mature in the bone marrow, T lymphocytes mature in the thymus gland
T lymphocytes
These are covered with receptors to bind to the specific antigens. There are: T helper cells, T killer cells, T memory cells and T regulator
T helper cells
These have CD4 receptors on their cell-surface membranes that bind the the antigens on an APC. They produce interleukins which are a type of cytokine. This stimulates the activity of B cells so that more antibodies are produced, and they attract more phagocytes to engulf the pathogens with antigen-antibody complexes attached to them.
T killer cells
These destroy pathogens carrying the antigen by producing perforin which makes holes in its cell membrane so it’s freely permeable. This will kill it
T memory cells
These live for a long time and are part of the immunological memory. They are created after the first time a certain pathogen has been encountered. if the pathogen enters again, they will divide rapidly into many clones of T killer cells and destroy them quickly.
T regulator cells
These cells will control and suppress the immune system. This means that when a pathogen has been removed and everything is normal, the immune system needs to be stopped. They also make sure the body can recognise a self antigen so it doesn’t produce an autoimmune response.
B lymphocytes
They are covered in antibodies that will bind with antigens. There are: Plasma cells, B effector cells and B memory cells
Plasma cells
This produces many antibodies for a specific antigen and releases them into the blood stream so they can produce an immune response. These don’t live long but they produce around 2000 antibodies.
B effector cells
These will divide to form clones of plasma cells