Name the 4 stages of immune response?
- Phagocytosis.
- T-cells.
- B-cells.
- Antibody Production.
What is a phagocyte?
Its a type of white blood cells that carries out phagocytosis.
Found in the blood and tissue and are the first cells to respond to an immune system trigger inside the body.
Describe the stages of phagocytosis.
Phagocyte recognises foreign antigen on pathogen.
Cytoplasm of phagocyte moves round pathogen- engulfing it.
Pathogen now contained in phagocytic vacuole in the cytoplasm of the phagocyte.
Lysosome fuses with phagocytic vacuole.
Lysozymes break down the pathogen.
Phagocyte then presents the pathogen’s antigens - sticks its the antigens on its surface to activate other immune system cells.
Phagocyte acts as an antigen-presenting cell.
What is a T-cell?
Another type of white blood cell.
It has receptor proteins on its surface that bind to complementary antigens presented to it by phagocytes.
This activates the T-cells.
Give an example of T-cell?
Helper T-cells release chemical signals that activate and stimulate phagocytes and cytotoxic T-cells, which kill abnormal and foreign cells.
TH cells activate B-cells which secrete antibodies.
What are B-cells?
Type of white blood cells.
Covered with antibodies - proteins that bind to antigens to form an antigen-antibody complex.
Each one has different shaped antibody on its membrane, so different ones bind to different shapes antigens.
Describe the process of clonal selection?
When the antibody on the surface of the B-cell meets a complementary antigen - it binds to it.
This, together with substances released from helper T-cells, activates the B-cells.
Activated B-cell divides into plasma cells?
What does an activated B-cell do?
Divided into plasma cells.
How are antibodies produced?
Plasma cells are identical to B-cells secrete loads of antibodies specific to the antigen.
These are called monoclonal antibodies.
They bind to the antigen on surface of pathogen to form loads of antigen-antibody complexes.
How does an antibody destroy pathogens?
Antibody has 2 binding sites, so it can bind to 2 pathogens at same time.
Meaning pathogens become clumped together - this is called agglutination.
Phagocytes bind to antibodies and phagocytose many pathogens at once.
This leads to destruction of pathogens.
Describe the structure of antibodies.
Proteins made up of chains of amino acids.
Secificty of antibody depends on its variable regions, which for antibody binding site.
Each antibody has a variable region with a unique tertiary structure thats complementary to one specific antigen.
What do antibodies have?
VARIABLE REGION - forms binding site and has a tertiary structure.
They have the same constant regions.
