Cell Recognition and the Immune System- The Immune System Flashcards
What are antigens?
Molecules (usually proteins) that trigger an immune response when detected by the body
Where are antigens found?
Usually on surface of cells
How are antigens used by the immune system?
To identify pathogens, abnormal body cells, toxins and non-self cells
What are the four main stages in the immune response?
- Phagocytes engulf pathogens
- Phagocytes activate T cells
- T cells activate B cells which divide into plasma cells
- Plasma cells make more antibodies to a specific antigen
How do phagocytes engulf pathogens (phagocytosis)?
- Phagocyte recognises foreign antigens on pathogen
- Cytoplasm of phagocyte moves round pathogen (engulfing it)
- Pathogen now contained in a phagosome
- Lysosome releases lysozymes which break down pathogen
- Phagocyte presents pathogen’s antigens
What is a phagocyte?
A type of white blood cell that carries out phagocytosis
Where are phagocytes found?
In blood and in tissues
What is a T cell?
A type of white blood cell
How are T cells activated?
The T cell has receptor proteins on its surface that bind to complementary antigens presented to it by the phagocytes
How can T cells respond?
TH cells (helper T cells) release chemical signals that activates and stimulates phagocytes and cytotoxic T cells (TC cells) which kill abnormal and foreign cells They can also stimulate B cells
What are B cells?
A type of white blood cell that secretes antibodies
What does it mean that antibodies are specific?
Each B cell has a different shaped antibody so different ones bind to different shaped antigens
What happens when antibodies bind to antigens?
An antigen-antibody complex is formed and B cells are activated (clonal selection) which divides into plasma cells
What do plasma cells do?
They secrete lots of antibodies specific to the antigen called monoclonal antibodies that bind to the antigen on the pathogens surface to form antigen-antibody complex
What is an antibody?
Proteins made up of chains of amino acids
