Immunology study guide for Quiz 1 Part 1 Introduction What is immunity Immunity is the ability of an organism to recognize and neutralize a foreign substance Examples Bacteria Fungi Viruses parasites tumor cells or biochemicals toxins The immune system protects against four classes of pathogen 1 Extracellular bacteria parasites fungi 2 Intracellular bacteria parasites 3 Viruses intracellular 4 Extracellular Parasites worms An antigen is a substance that has the potential to elicit an immune response An immunogen is a substance that has already generated an immune response There are two categories of immunity 1 Nonspecific Innate Natural Native Immunity is always present repeated exposure does not increase response It is a property of all living organisms Examples Biochemical in blood tears saliva skin secretions certain blood and tissue cells a Innate immunity generally responds to general pathogens 2 Specific Adaptive Acquired Immunity Found in vertebrates and a few other organisms a Recognition can be very specific b Repeated encounters evoke stronger and more efficient responses Immunological memory c Basis of immunization There are two arms of Effectors of specific immunity 1 Humoral mediated by antibodies responsible for detecting and destroying antigens on or outside of cells humoral effectors float around in body fluids like lymph ect 2 Cellular mediated by cells responsible for detecting and destroying antigens inside of the cell Example lymphocytes Each arm can recognize and discriminate between billions of different antigens Immunoglobulin Ig structure and antigen Ag terminology Immunoglobulin is another name for antibodies These are effector molecules Antibodies Abs are the effectors of humoral immunity The epitope is the area where the Abs targets the molecule The Lymphocyte is the effector of cellular immunity The History of Immunology The earliest efforts in immunology were based on folk medicine In the 1500s Indians Asian inhaled smallpox scabs In 1720 Lady Montague A member of English royalty observed the practice in turkey and brought it to England In 1796 Edward Jenner discovered vaccination He noticed that milkmaids who had gotten cowpox did not get smallpox This phenomenon is cross reactivity Ab against one agent cross reacts with a related agent i e the two agents are biochemically similar enough that the Ab can see both Jenner deliberately exposed patients to cowpox then challenged them with smallpox Predicted that his technique would wipe out smallpox He was right but it took 182 years Benjamin Jesty was an English farmer who deliberately exposed his wife and sons to cowpox both were later exposed to smallpox without effect He predated Jenner by 20 years but he was not widely known In the 1880 s Louis Pasteur The father of immunology worked with chicken cholera rabbits He used attenuated cultures weakened cultures as vaccines The first person to be vaccinated was Joseph Meister Elie Metchnikoff a Russian zoologist in the 1880 s asked the question What is the basis of immunity He observed cells in tissues attacking bacteria and other foreign objects He termed them macrophages and microphages Now called neutrophils He declared that these cells were the basis for immunity Emile Roux and Alexandre Yersin In 1888 they neutralized diphtheria and tetanus toxins with antisera to toxoids partially denatured toxins They demonstrated in vitro neutralization therefore cells could not be the basis of immunity Experiment In vitro neutralization Temporary protection 1 They injected an animal with a toxin The animal died 2 They injected the animal with a toxoid The animal did not die 3 The combined the serum of the toxoid injected animal with the toxin and injected this cocktail into a new animal and there is no harmful effect Key here is that the serum does not contain cells The animal lived The antibodies in the serum neutralized the toxin This experiment demonstrated that the cells are not the basis of immunity Emil von Behring and Shibasaburo Kitasato In 1890 described passive immunity Antiserum to diphtheria and tetanus toxin protected animals when injected prior to bacterial or toxin exposure neutralization Passive immunity In vivo Experiment Temporary Protection 1 Injecting the animal resulted in a dead animal same as in last experiment 2 They injected an animal with toxoid the animal did not die and then they took serum from that animal 3 Instead of mixing the serum with a toxoid they injected just the serum into a different animal 4 After a period of time they injected the animal with the toxin and the animal survived The animal does not develop memory because the immunity was acquired from the serum which has no cells only molecules and the molecules have finite half life in the order of weeks Once the antibodies decay there is no more immunity Paul Ehrlich s side chain theory 1896 Proposed that cells produce side chains What we now recognize as antibodies that have varying specificities Antigen binds specific side chain and induces increased production and secretion He imagined that there must be cells in the body that had complimentary molecules on their surface to the toxin There must be some interaction between the toxin and the side chain that would stimulate the cell to produce more side chains Cellular immunity rediscovered Sir Peter Brian Medawar RAF in the 1940 s WWII He was a flight surgeon and was faced with the treatment of a lot of burn victims He experimented with tissue grafts and observed the following If he gave patient a skin graft and if was not from the patient himself an allograph it would eventually be rejected become necrotic and slough off This would happen even if the graft was taken from a live donor If he tried to de a second graft from the same donor the graft would be rejected much more quickly than the first time If the second graph was not from the same donor it would be rejected just as slowly as the first graft Due to immunological memory He determined that this was an immunological issue and he was able to demonstrate that there were no antibodies involved Experiment Adoptive transfer of immunity permanent protection The mice in this experiment must be genetically identical animals and the graft comes from a genetically unrelated individual 1 He performed a tissue graft on an animal and the grafts was rejected after 2 weeks 2 He performs a skin graft on an animal waits 2 weeks for the graft to be rejected and then he takes out