Cell recognition and the immune system

• • Recognising ‘foreign’ cells and targeting any pathogenic cells, a process known as a specific immune response
• • This ability to recognise ‘foreign’ cells is made possible by specific molecules found on the surface of cells (and viral particles) that enable them to be identified by the body. These molecules re usually proteins. such as glycoproteins.
• What do the surface proteins found on cells allows the body to recognise?

  1. Pathogenic cells
  2. abnormal body cells
  3. cancerous cells
  4. toxins
  5. cells from other individuals from the same species.
• Define antigen

  Surface molecules on viral particles and toxins. They allows cell-to- cell recognition.
• Antigens can either be...

  Self antigens - do not stimulate an immune response

  non-self antigens - stimulate an immune response
• What is phagocytosis

  A process carried out by a specific white blood cells (Phagocyte). It’s the process of recognising and engulfing a pathogen.
• What are the two steps of lymphocytes

  T-lymphocytes (T cells)

  B-lymphocytes (B cells)
• T-lymphocytes and the cellular immune response

  Immature T-lymphocytes leave the bone marrow to mature in the thymus

  T-lymphocytes are activated when they bind to their specific antigen that is being presented by the host cell.

  the antigen-presenting cell may be a:

  • Macrophage (phagocyte)
  • body cell that has been invaded by a pathogen and is displaying the antigen on its cell surface membrane
• What are the two types of T-lymphocytes?

  1. Helper T cells
  2. cytotoxic T cells
• Helper T cells

  Release cytokines which stimulate:

  • the maturation of B-lymphocytes into antibody-secreting plasma cells
  • the production of memory B cells
  • the activation of cytotoxic T cells
• how do cytotoxic T cells kill infected cells

  Cytotoxic T cells produce a protein called perforin. These make holes in the cell surface membrane. These holes mean the cell-surface membrane becomes freely permeable.
• What type of immunity/ response are T-lymphocytes apart of?

  Cell-mediated immunity/ cellular response
• Structure of an antibody

  Globular glycoprotein called immunoglobulins

  have a quanternary structure: two heavy (long)polypeptide chains bonded by disulfied bonds to two light (short) polypeptide chains.

  each polypeptide chain has a constant region and a variable region
• name the missing labels

  1. Disulfide bonds
  2. heavy (long) polypeptide chain
  3. Light (short) polypeptide chain
  4. constant region
  5. variable region

  
• Explain how HIV affects the production of antibodies when AIDS develops in a person.

  1. Less/ no antibody produced
  2. because HIV destroys helper T- cells
  3. few/ no B cells activated/ stimulates

  or

  (So) few B cells undergo mitosis/ differentiate/ form plasma cells
• Using the graph below, what can you conclude about the effectiveness of each injection on the immune response of these mice?

  1. Mean antibody concentration increases
  2. 1st injection protects som mice

  1st injection causes primary immune response

  3. 2nd/3rd injection protects most mice - causes secondary immune response - uses memory cells

  4. Antibody decreased rapidly after 3rd injection

  5. no mice protected after 180 days/ vaccine not effective in long term/ booster required