Immune System Specific Immunity General Aspects of Specific Immunity Specific Immunity Cellular immunity Cell mediated T cells immunity Antigen Presenting Cells T Lymphocytes directly attack diseased body cells 19 1 Specific Immunity The Third Line of Defense The specific immune system recognizes specific foreign substances and acts to neutralize destroy them Specific immune system consists of adaptive immune responses unlike th einnate immune responses and nonspecific immune system Specificity and memory Immune function is directed against a particular pathogen When re exposed to the same pathogen the specific immune response occurs quite quickly and often so fast the second time around that no noticeable illness develop Unlike nonspecific immune responses such as inflamm which have the same rxn time bc they are not changed by repeated exposure to the same pathogen 19 2 Specific Immunity These two forms interact and they often respond to the same pathogen Cellular immunity cell mediated T cells T Lymphocytes directly attack diseased body cells fighting pathogens that reside inside body cells Viruses some bacteria and yeast protozoans Cell mediated immune responses attack cancer cells and cells of transplanted tissues and organs Humoral immunity antibody mediated B cells antibodies produced by B lymphocytes that do not directly destroy a pathogen but tag them for destruction Works only against the extracellular stages of infectious organisms Effective against EC viruses bacteria yeast protozoans as well as toxins venom and allergens Microbes are only vulnerable to attack by cellular immunity when microbes invading body cells 21 3 Antigens Molecule that triggers an immune response Some are free floating molecules such as venoms and toxins while others are parts of the plasma membrane or walls of bacterial cells or protein coat of a virus Small molecules like glucose and amino acids are not antigens Most antigens large complex molecules proteins polysaccharides glycoproteins glycolipids Epitopes antigenic determinants region of the antigen molecule that generates immune response The immune system learns to distinguish self from non self prior to birth and normally attacks only non self antigens Typically an antigen is any non self or foreign molecule which can 21 4 induce a specific immune response Active and Passive Immunity Active natural immunity produces memory cells production of body s own antibodies or T cells as a result of natural exposure to antigen during infection Active artificial immunity produces memory cells production of body s own antibodies or T cells as a result of artificial exposure to an antigen due to vaccination A vaccine is dead or attenuated pathogen which can generate an immune response without causing the disease Passive natural immunity temporary immunity body acquires antibodies produced by another person through placenta or milk Passive artificial immunity temporary immunity body acquires antibodies produced by another person or animal by an injection of an immune serum Immune serum is used for emergency treatment of botulism snakebite tetanus rabies and other diseases 21 5 Lymphocytes B and T Lymphocytes are essential cells to specific Each B or T lymphocyte is specific for just one type of NK cells act nonspecifically but are affected by specific immune function antigen immune responses B and T cells are produced in the red bone marrow as descendants of pluripotent stem cells B cells mature or become immunocompetent in bone marrow while T cells mature in thymus Immunocompetent means able to recognize and respond to antigens but have not encountered nonself or foreign antigen yet Immunocompetent B and T cells are only activated when exposed to antigens 21 6 Life Cycle of T cells Mature in thymus Thymosin thymic hormone stimulates maturing T cells to produce surface antigen receptors With receptors T cells are capable of recognizing Tested to recognize self MHC antigens on the reticular epithelia in thymus T cells fail if do not recognize self antigens or react to self A very small of T cells usually pass and are not antigens antigens eliminated B cells are also tested against self antigens as well 21 7 T and B Lymphocytes Mature but na ve B and T cells can disperse throughout the body via blood and lymph to lymph nodes spleen tonsils and mucus membranes linings of digestive respiratory urinary and reproductive tracts Most lymphocyte traffic is between secondary lymph organs lymph blood and tissues of body T and B cell activation occurs in secondary lymphatic organs 19 8 Lymphocytes During cell maturation random DNA rearrangement in genes that code for receptors and antibodies leads to millions of distinct T cells or B cells and their clones as well as many distinct antibodies from distinct B cells Each mature T cells and B cell acquire receptors that can bind to only one specific antigen These distinct cells and their clones possess receptors of singly specificity This ensures that the vertebrate animal is ready for any of the vast number of different antigens the vertebrate may encounter in its lifetime 19 9 Specific Immune Response recognition of a specific antigen by lymphocytes activation of lymphocytes the attack launched by lymphocytes and their secretions the ability to remember exposure to an antigen lymphocytes and APCs use interleukins a type of cytokine to communicate stimulate cells that secrete them and stimulate other WBCs also affect neighboring cells 21 10 Cellular Immunity Four classes of T cells Cell mediated immunity a form of specific defense in which T lymphocytes directly attack and destroy diseased body cells Cytotoxic T cells Tc cells attack diseased body cells called killer T cells because they directly kill their specific target cell but not same as NK cells which are non specific Helper T cells TH cells help promote Tc cell and B cell action and nonspecific defense mechanisms Regulatory T cells limit immune response by inhibiting cytokine secretion by other T cells Memory T cells provide memory for immune response after exposure to a particular antigen T cells have CD glycoproteins which are cell adhesion molecules that enable T cells to bidn to other cells 21 11 Antigen Presenting Cells APCs Critical to assisting T cells to recognize foreign antigens and diseased and cancerous body cells Dendritic cells macrophages and B cells are typical APCs Any cell in body which is cancerous or infected by a virus can act as an APC