cell recognition MS

• what can molecules on the surface identify:

  • pathogens
  • cell from other organisms of the same species (transplants)
  • abnormal body cells (cancer cells) 
  • toxins
• antigen:

  glycoprotein that stimulates an immune response/ production of an antibody
• antigen variability

  pathogens that mutate frequently causing shape of the antigen to change

  • causes previous immunity to be ineffective as the memory cells won't have the memory of the new antigen shape
• Describe how a phagocyte destroys a pathogen present in the blood.

  1. Engulfs

  2. Forming vesicle and fuses with lysosome; 

  3. Lysozymes digest & hydrolyse; 
• T-cells:

  made in the bone marrow

  matures in the thymus
• cell-mediated response:

  • when pathogens is destroyed via phagocytosis, the antigens are presented on the phagocyte (APC)
  • helper T cells have receptors that attach to the antigen of APC
  • attachment activates T cells to divide rapidly via mitosis - replicates and forms clones
  • cloned helper T cells differentiate into:
  • develop to memory cells
  • stimulates B cells to divide
  • stimulates phagocytosis 
  • activates cytotoxic t cells
• cytotoxic t cells

  can kill abnormal/infected cells

  • produces protein (perforin) creates pores - causes a freely permeable membrane
  • causes cell death
• B cells:

  made and maturated in the bone marrow
• B cell activation

  antigen that is complementary to a B cell antibody is taken via endocytosis and presented on the surface

  • helper T cell binds to B cell - activating the stimulation of B cells to divide by mitosis (differentiate to memory b cells/plasma cells(clonal selection)
• antibody:

  an immunoglobulin that is specific to an antigen and is produced by B cells
• agglutination:

  antibodies binds to antigen forming an antibody-antigen complex

  • antibodies can attach to various antigens and clump together
• memory B cells

  secondary immune response

  • live for decades
  • can divide via mitosis and make plasma cells rapidly when encountering a previous antigen
• plasma cells

  produces antibodies that can destroy pathogens
• process of a vaccine

  1. Vaccine contains antigen from pathogen; 

  2. Macrophage presents antigen on its surface; 

  3. T cell with complementary receptor protein binds to antigen; 

  4. T cell stimulates B cell; 

  5. (With) complementary antibody on its surface; 

  6. B cell secretes large amounts of antibody; 

  7. B cell divides to form clones all secreting / producing the same antibody.
• herd immunity:

  if enough of the population is vaccinated - pathogens cant spread easily (provides protection)
• difference between active and passive immunity.

  1.Active involves memory cells, passive does not; 

  2. Active involves production of antibody by plasma cells & memory cells; 

  3. Passive involves antibody introduced into body from outside

  4. Active long term, because antibody produced in response to antigen; 

  5. Passive short term, because antibody is broken down; 

  6. Active take time to work, passive fast acting.
• Describe how HIV is replicated.

  1. Attachment proteins attach to receptors on helper T cell
  2. RNA enters cell; 
  3. Reverse transcriptase converts RNA to DNA; 
  4. Viral protein produced; 
  5. Virus assembled and released from cell
• monoclonal antibody

  (Antibody produced from) identical/cloned plasma cells/B cells/B lymphocytes;
• direct monoclonal antibody therapy:

  • monoclonal antibodies that are specific to antigens 
  • preventing chemical signals that stimulate uncontrolled cell division
• indirect monoclonal antibody therapy

  • attachment of cytotoxic drug to the antibody so the antibody attaches to cancer cells and kills it
• ethical issues of monoclonal antibodies

  formed from mice as they produce antibodies and tumour cells
• Describe the role of antibodies in producing a positive result in an ELISA test.

  1. First antibody binds to antigen - complementary in shape
  2. Second antibody with enzyme attached is added; 
  3. Second antibody attaches to antigen;
  4. wash off excess antibodies
  5. Substrate added and colour changes;
• primary response:

  • first exposed to a pathogen (antigen)
  • takes longer for antibodies to be produced - slower response
• secondary response

  • memory B cells, create antibodies much quicker
• passive immunity

  • antibodies - introduced to the body
  • no long term immunity
• Explain how HIV affects the production of antibodies when AIDS develops in a person.

  • Less/no antibody produced;
  • (Because HIV) destroys helper T cells; Accept ‘reduces number’ for ‘destroys’
  • (So) few/no B cells activated / stimulated OR (So) few/no B cells undergo mitosis/differentiate/form plasma cells;