The Immune System 2C Flashcards
What is an antigen
molecules (usually proteins) that generate an immune response when detected by the body
Where are antigens found
surface of cells
What are antigens used for
Used by immune system to identify pathogen, abnormal body cells, toxins and cells from other individuals of the same species eg organ transplants
What is a phagocyte
a type of white blood cell which carries out phagocytosis they are found in in the blood and are in tissues
How do phagocytes work
- A phagocyte recognises the foreign antigen on a pathogen
- Cytoplasm of the phagocyte moves round the pathogen, engulfing it
- The pathogen in now contained in a phagocytic vacuole in the cytoplasm of the phagocyte
- A lysosome fuses with the phagocytic vacuole. The lysozymes break down the pathogen
- The phagocyte then presents the pathogen’s antigens - it sticks the antigens on its surface to activate other immune system cells
What do phagocytes active
T-Cells
What is a T Cell
A type of white blood cell
What do receptor proteins on T cells do
Bind to complementary antigens presented to it by phagocytes
What do helper T cells do
Release chemical signals that activate and stimulate phagocytes. They can also activate B cells
What do cytotoxic T cells do
They kill abnormal and foreign cells
What are B cells
A type of white blood cell
What are B cells covered with
antibodies. Each B cell has a different shaped antibody on its membrane , so different ones bind to different shaped antigens
What are antibodies
Proteins which bind antigens to form an antigen antibody complex. Made
up of chains of amino acids. Each antibody has a different variable region with a different tertiary structure All antibodies have the same constant regions
Describe clonal selection
when an antigen- antibody complex is formed and the substances released from helper T cells activates the B cell. This activated B cell divides into plasma cells
What do you call two cells that are identical to each other
clones. For example, plasma cells and B cells are clones
How many binding sites does an antibody have
2, so an antibody can bind to two pathogens at once
Define agglutination
when pathogens become clumped together phagocytes then bind to the antibodies and phagocytose many pathogens at once this leads to the destruction of pathogen carrying this antigen in the body
Define Cellular immune response
The T - cells and other immune system cells they interact with.
Define Humoral immune response
B-cells, clonal selection and the production of monoclonal antibodies
The primary immune response
When an antigen enters the body for a first time
Not many B cells that can make the antibody need to bind to the antigen, eventually the body will produce enough of the right antibody to overcome the infection. Meanwhile, the person will show symptoms
After being exposed to the antigen both T- cells and B- cells produce memory cells which remain in the body for a long time. Memory T- cells remember the specific antigen and will recognise it a second time. Memory B- cells record the specific antibodies needed to bind the antigen
The person is now immune - their immune system has the ability to respond quickly to a second infection
Secondary immune response
Same pathogen enters the body again and the immune response is quicker.
Clonal selection happens faster. Memory B- cells are activated and divide into plasma cells that produce the right antibody to the antigen. Memory T- are activated and divide into the correct type of T- cells to kill the cell carrying the antigen
The secondary response often gets rid of the pathogen before you begin to show any symptoms - you are immune to the pathogen
