Lecture 19 BIO 311D 1st EditionOutline of Last Lecture I. Antimicrobial peptides and proteinsII. Inflammatory ReponsesIII. Evasion of Innate Immunity by pathogensIV. Antigen by recognition T CellsV. Immuniology memoryVI. B and T cell developmentOutline of Current Lecture I. Origin of Self-ToleranceII. Proliferation of B Cells and T CellsIII. Immunological MemoryCurrent LectureEven when _______ is implanted multiple times into a vertebrate body, it would likely fail to provoke production of antibodiesA. A pathogenic virusB. A nonpathogenic bacteriumC. A protein toxinD. A plastic beadE. A piece of plant leafOrigin 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 nonfunctionalProliferation 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 againImmunological 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
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