cellular immune response

• lymphocytes (B and T cells) are white blood involved on the specific immune response
• cell mediated response is the response involving T cells and body cells
• antigen presenting cell (APC) is any cell that presents a non-self antigen on their surface - e.g. macrophage, cells of a transplanted organ
• The cell mediated response:

  1. once pathogen has been engulfed and destroyed by the phagocyte the antigens are positioned on the surface = now called antigen presenting cell
  2. Helper T cell have receptors on their surface which can attach to the antigens on APC
  3. once attached this activates Helper T cells (clonal selection) to divide by mitosis to replicate and make large number of clones
  4. cloned Helper T cells differentiate into different cells - helper t cells, cytotoxic t cells etc
• cytotoxic T cells destroy abnormal or infected cells by releasing protein perforin embedding in the cell surface membrane and makes a pore so any substance can enter or leave leading to cell death
• cell mediated response

  
• Types of white blood cells:

  • phagocytes (non - specific)
  • lymphocytes (specific)
• a phagocyte is a macrophage that carries out phagocytosis
• non-specific means the pathogen/ non-self cell that is detected will trigger the SAME response to destroy it = doesn't differentiate
• Phagocytosis:

  1. phagocytes in the blood are attracted to the chemical/antigen released by the pathogen - the phagocyte will move towards the cell along a conc gradient
  2. phagocyte has many receptors on surface which attach to the chemicals/antigens on the pathogen
  3. the phagocyte changes shape to engulf the pathogen during endocytosis
  4. the pathogen is contained within a phagosome vesicle for lysosomes to migrate towards and fuse to release enzyme lysozymes
  5. lysozymes hydrolyse and destroy pathogen releasing it by exocytosis but keep some antigens to present on surface - (APC)
• Each type of cell has specific receptors on its surface that identify it (proteins) enable the immune system to identify:

  • pathogens

  • cells from other organisms of the same species

  • abnormal body cells

  • toxins.
• type of cloned T cell:

  • T helper cells = release chemicals to activate B lymphocytes.
  • T killer cells (aka cytotoxic T cells) = destroy any cells which have been infected with the pathogen
  • T memory cells = remain in the bloodstream in readiness to respond to a future infection by same pathogen