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4.6.9 The roles of B cells and T cells in the body’s immune responce

There are two different types of Immune Response; A Cell-mediated Immune Response

B             Antibody-mediated Immune Response.

 

NB: ISOLATED VIRUSES DO  NOT PRESENT ANTIGENS AND THEREFORE DO  NOT TRIGGER EITHER THE CELL- OR ANTIBODY-MEDIATED IMMUNE RESPONSE. HOWEVER, WHEN VIRUSES INVADE HOST CELLS, VIRAL  PROTEINS ARE EXPRESSED WHICH BECOME   INCORPORATED

INTO THE HOST CELL SURFACE MEMBRANE VIA MHC. THESE PROTEINS ARE RECOGNISED AS ANTIGENS.

Cell-Mediated Immune Responce

  1. Competent T Cells recognise a specific foreign antigen using its T cell receptor.

 

  1. Activated T Cell undergoes rapid mitosis forming a large number of identical clone T

 

  1. Cloned T Cells differentiate into Killer, Helper, Memory or Suppressor T

 

  1. Killer and Helper Cells migrate to the site of infection

 

Killer T Cells: attach to the infected / foreign cell and release the enzyme Perforin, which makes holes in the pathogen’s cell membrane causing it to die

 

Helper T Cells: stimulate B cells to start producing antibody and attract macrophages to the site of infection

Memory T Cells: remain in the lymph nodes. They will respond rapidly if the same pathogen invades the body again, because they have the right T cell receptor to recognise the pathogen. This means that the body can mount an immune response before infection becomes serious

 

Suppresor T Cells: stop the immune reaction after about a week

 

AntiBody-Mediated Immune Responce:

  1. B cells are recognise a specific foreign antigen using the antibody molecules on their surface. B cells can also be activated by macrophages & Helper T cells. When a macrophage digests a pathogenic cell antigens from the cell membrane get stuck in the macrophage’s membrane; any B Cells which come into contact with the antigen will then be activated

 

  1. The activated B cell undergoes rapid mitosis and lots of clone B cells are produced

 

  1. Cloned B Cells differentiate into either Plasma or Memory cells

Plasma Cells

  1. Plasma cells antibody, which is specific for one antigen only
  2. Antibody is transported via the lymph to the site of infection
  3. Antibody attaches to the specific antigen
  4. An antigen-antibody complex is formed

Memory Cells

Memory Cells continue to secrete antibody for many years, so that if the body is infected by the same pathogen the Memory B cells can produce an instant supply of antibody before the infection becomes serious.