Cell mediated response

• define immunity


  the ability to resist infection
• where are B lymphocytes matured and which response do they take part in?

  bone marrow - humoural response
• where are T lymphocytes matured and what response to they partake in?

  thymus - cell mediated response
• describe how T cells mature to produce cells with different receptors


  immature T cells divide by mitosis in the bone marrow (clonal selection occurs)

  in thymus the T cells are matured

  T cells produce receptors

  mature T cells with different receptors are produces
• what 2 types of cells do T cells differentiate into?

  T helper cells

  cytotoxic T cells
• which response are T lymphocytes involved in?

  cell mediated
• describe the stages of response of the helper T cells

  1. pathogen invades the cells
  2. phagocytes place antigens from pathogen on its cell surface membrane
  3. receptors on specific T cell fit onto antigens
  4. attachment activates T cell to divide rapidly by mitosis and form clone of cells
  5. cloned cells release cytokines
• how do the T helper cells assist wbcs in initiating immune response?

  they release cytokines which activate cytotoxic T cells and stimulate memory cells
• what is the function of the cytokines?

  develop memory cells

  stimulate phagocytes

  stimulate B cells to divide

  activate cytotoxic T cells
• how to cytotoxic T cells kill infected cells ?

  vacuoles contain toxins which are secreted into infected cell - punches holes in the membrane
• how to cytotoxic T cells kill infected cells ?

  vacuoles contain toxin perforin which are secreted into infected cell - punches holes in the membrane
• why are T cells most effective against viruses?

  because viruses replicate inside cells
• describe the function of a cytotoxic T cell

  T cell receptors bind to cell

  vesicles containing toxins are released into the affected cell via holes the T cell creates in membrane

  Toxins kill cell
• describe the cell mediated response


  1 helper T cells bind to antigens on B cells causing them to clone into memory/ plasma cells

  
  

  2 can release chemicals which attract phagocytes

  
  

  3 stimulate cytotoxic T cells
• describe the cell mediated response

  naive helper T cells receptors bind to an antigen on an antigen presenting cell this stimulates the helper T cell to clone it self

  
  

  the clone helper T cells stimulate B cells to clone phagocytes to undergo phagocytosis and cytotoxic T cells to target infected cells

  
  

  cytotoxic T cells bind to infected cells and release perforin