L#1 & #2: Introduction to the Immune System
L#1 & #2: Introduction to the Immune System 0530
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This 2 page Class Notes was uploaded by Denise Croote on Wednesday January 20, 2016. The Class Notes belongs to 0530 at Brown University taught by Dr. Richard Bungiro in Fall 2013. Since its upload, it has received 25 views. For similar materials see Principles of Immunology in Biology at Brown University.
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Amazing. Wouldn't have passed this test without these notes. Hoping this notetaker will be around for the final!
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Date Created: 01/20/16
Lectures One & Two: Introduction to Immunology Immune System Basic Function: resist diseases caused by….. A. Viruses- replicate inside of the host’s cells and require the host cell’s machinery B. Bacteria- can infect intracellularly or extracellularly C. Fungi – most homogenous in form but can usually be kept in check by the innate immune system D. Parasites – are the most heterogenous in form. The can be a single celled organism or a multicellular worm. They can go through several lifecycles inside the human and require the immune system to change its approach. Small pox is caused by the variola virus. Once infected 30% of those who contract it die from it. o Society’s response was to variolate - inject a small portion of the disease from a sick individual to a healthy individual. This caused a local response and induced immunity, but was risky because a full blown smallpox response could have resulted. o Jenner introduced a vaccination. He injected individuals with the vacccinia virus from cowpox because it was closely related to the variola virus and could produce a cross protective immune response. Advantage: no chance of contracting smallpox. Louis Pasteur determined that weakening or attenuating a virus could mount an immune response and provide immunity without killing the patient (introduction of vaccines). Two Major Types of Immunity: o Humoral – the antibodies are in the serum, those who supported this theory noticed that fluid fractions (without cells) from animals immunized against a certain bacteria could transfer the immunity to others 1. Bell cell produces and releases antibodies o Cellular – those who believed in this theory noticed that animals immunized against a bacteria had more active phagocytes 1. T cells secrete cytokines and turn into infected cell killers Antibodies are specific to the antigen they bind to. Where does this specificity come from? o 1.) Selective Theory: cells have a series of different side chains and when an antigen approaches it binds to a side chain. The side chain it selects is then replicated on the cell surface so it can bind to more antigens, and released into the fluid. (WRONG) o 2.) Instructional Theory: antibody folds and molds itself around the antigen. (WRONG) o 3.) Clonal Selection Theory: a lymphocyte is specific to one type of antigen, when the antigen binds that cell proliferates and makes clones of itself, all with the same affinity for the same antigen (RIGHT). Characteristics of Innate Immunity: o First line of defense o Responds quickly within minutes to hours o Does not improve with time or exposure o Stalls the infection and activates the adaptive immune system o Recognizes fixed patterns shared by many pathogens o Could be in the form of anatomical barriers, phagocytic cells, soluble mediators, and inflammatory responses o All vertebrates and multicellular organisms have it Why do we need an adaptive immune response if we have the innate immune response? o Infectious organisms can rearrange their genomes rapidly and evolve to circumvent our innate defenses o Our adaptive response is made of cells that are plastic and can change to counter the invasion strategies of the microbe Characteristics of Adaptive Immunity: o Much slower to respond, requires days to weeks to activate o Is used to eliminate the pathogen if the innate response fails to do so o Specifically recognizes certain pathogens o Is mediated by B and T lymphocytes, Antigen Presenting Cells, Dendritic cells, and Macrophages 1. Defining Characteristics 1.) Specificity – the adaptive response can distinguish between various antigens produced by a pathogen because it is comprised of ARMS, immunoglobulins, and T cell Receptors 2.) Diversity – capable of reacting with an unlimited variety of antigens because of the wide range of genetic variability among the DNA 3.) Memory – can remember a pathogen and mount a quicker more effective immune response the second time 4.) Self/NonSelf Recognition – can eliminate foreign molecules without bringing harm to one’s own tissues. So what types of cells mediate this immune response? o Antibodies: these can also be called immunoglobulins, they are produced by B cells and may be surface bound or secreted, the recognize native antigens o Antibodies can travel as soluble molecules in the blood fluid, or could attach to a membrane. o Antibodies have 2 heavy chains and 4 light changes in their structures o T Cell Receptors: Produced and present on cytotoxic T cells and helper T cells. They are ONLY surface bound and they recognize processed antigens on specialized MHC molecules. o Require an MHC molecule to present a part of the Antigen to the T cell. o MHCII molecules are present on professional APCs (which include B cells, macrophages, and dendritic cells) o MHCI are produced by almost all nucleated cells ** These receptors are diverse and have the ability to recognize a wide variety of pathogens, even those not yet seen by the body (because of gene rearrangement). PRRs (which are the receptors involved in the innate response to PAMPS aren’t as specific). What happens when a good immune system goes bad? o allergies and asthma are result of a overly sensitive immune repose o Can cause graft rejections (failure to transplant) because donor antibodies will attack recipient antigens and vice versa. o Autoimmune diseases – you go after yourself o Immunodeficiency lack of response 1. Can be inborn ex.) SCID – severe combined immunodeficiency 2. Or can be acquired – HIV and AIDS
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