immune system

• what is the non specific immune response?

  immediate response which is the same for all pathogens

  • physical barriers and phagocytosis
• what is the specific immune response?


  slower response adapted for each specific pathogen

  • T - cells: cell mediated response
  • B - cells: humoral response
• what is an antigen?

  A foreign/non - self protein that generates an immune response/production of antibodies.
• what happens once a pathogen has enetered the body?

  pathogen releases chemicals and debris. this attracts the phagocyte to move towards it

  phagocyte recognises it, receptor cells of the phagocyte bind to the antigen on the pathogen

  phagocyte engulfs it and it changes shape

  engulfed pathogen is contained within a phagosome vesicle

  lysosomes within the phagocyte fuses with the vesicle

  lysosomes contain lysozymes (hydrolytic enzymes)

  these lysozymes digest/destroy the pathogen by hydrolysis

  soluble products are absorbed by phagocyte

  antigen is presented as an antigen presenting cell
• In the specific immune response, T-cells play a crucial role:
• Pathogens invade body cells and are engulfed by phagocytes, which then become antigen-presenting cells
• Receptors on the helper T-cell are complementary to these antigens, activating the T-cell
• The helper T-cell divides rapidly by mitosis, forming a clone of genetically identical cells
• The cloned helper T-cell can differentiate into: B-cell, phagocyte, memory cells, cytotoxic T-cells
• TH cells release chemicals (cytokines) that activate cytotoxic T-cells, which then destroy infected body cells
• Cytotoxic T-cells release perforin, creating a pore in the cell membrane of the infected cell, causing it to shrivel and die
• What happens to some of the body's healthy cells in T-cells?

  destroyed and sacrificed to prevent further replication.
• when a T - cell is cloned it may differentiate into which type of cell?

  B cell
• how are B cells activated?

  a complementary receptor on a specific B cell will bind to its specific antigen and this is activated by chemicals released by Th cells.
• explain the primary response of a B cell?

  the activated B cell than divides rapidly by mitosis to form a clone via clonal selection

  they will develop into one of two types of cell: plasma cells or memory cells

  primary response: plasma cells secrete antibodies - they make specific antibodies for specific antigens

  secondary response: memory cells - encounter the same antigen at a later date they:

  divide rapidly

  produce large numbers of memory and plasma cells

  large numbers of plasma cells means more antibodies will be produced faster
• how are antibody - antigen complexes formed?


  Antibodies have specific shapes and structure

  they bind to its complementary antigen

  forming antigen - antibody complex

  they have specific tertiary structure and shape
• annotate the antibody diagram?

  two binding sites

  4 polypeptide chains

  antigen binding site

  light chain + heavy chain

  disulphide bond

  constant portion

  variable portion

  
• what are antibodies?

  proteins synthesised by B cells specifically plasma cells
• how does agglutination occur?

  occurs when an antibody - antigen complex forms

  pathogen becomes clumped together

  these clumped pathogens attract phagocytes

  phagocyte moves towards them

  then are engulfed by the phagocyte
• describe two differences and two similarities of antibodies and antigens?

  antigen generates an immune response however an antibody is part of the body's immune response

  antigen is found on the surface of cells

  antibodies are secreted by plasma cells

  BOTH:

  proteins with specific tertiary structures

  involved in the immune response