Lecture 19 BIO 311D 1st Edition Outline of Last Lecture I Antimicrobial peptides and proteins II Inflammatory Reponses III Evasion of Innate Immunity by pathogens IV Antigen by recognition T Cells V Immuniology memory VI B and T cell development Outline of Current Lecture I Origin of Self Tolerance II Proliferation of B Cells and T Cells III Immunological Memory Current Lecture Even when is implanted multiple times into a vertebrate body it would likely fail to provoke production of antibodies A A pathogenic virus B A nonpathogenic bacterium C A protein toxin D A plastic bead E A piece of plant leaf Origin of Self Tolerance Antigen receptors are generated by random rearrangement of DNA As lymphocytes mature in bone marrow or the thymus they are tested for self reactivity Some B and T cells with receptors specific for the body s own molecules are destroyed by apoptosis or programmed cell death The remainder are rendered nonfunctional Proliferation of B Cells and T Cells In the body there are few lymphocytes with antigen receptors for any particular epitope In the lymph nodes an antigen is exposed to a steady stream of lymphocytes until a match is made This binding of a mature lymphocyte to an antigen initiates events that activate the lymphocyte Once activated a B or T cell undergoes multiple cell divisions This proliferation of lymphocytes is called clonal selection Two types of clones are produced short lived activated effector cells that act immediately against the antigen and long lived memory cells that can give rise to effector cells if the same antigen is encountered again Immunological Memory Immunological memory is responsible for long term protections against diseases due to either a prior infection or vaccination The first exposure to a specific antigen represents the primary immune response During this time selected B and T cells give rise to their effector forms In the secondary immune response memory cells facilitate a faster more efficient response
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