2422011FallOutlC21Part2

2422011FallOutlC21Part2 - 21: The Immune System: Innate and...

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21: The Immune System: Innate and Adaptive   Body Defenses PART 2: ADAPTIVE DEFENSES [ACQUIRED OR SPECIFIC IMMUNITY] (pp. 775–895; Figs. 21.7– 21.22) III. Antigens (pp. 776–777; Fig. 21.7) A. Aspects of the Adaptive (also called acquired or specific immunity) Immune Response   1.    Adaptive  (acquired) immunity  is considered  the third  line of defense after intact skin/mucous   membranes                              and  innate immunity. 2. The adaptive defenses recognize and  destroy  the  specific  antigen  that initiated  the response. 3. The immune  system  must  be ready  to confront  any  antigen  at any  time and  its  versatility  results in part   from the large diversity of lymphocytes present  in the body, and  in part from the variability of the   synthesized  antibodies.  4. The immune  response is a  systemic  response; it is not limited  to the initial infection site. 5. The immune  system  also exhibits  tolerance . 6. After an initial exposure  the immune  response  is able to recognize the same antigen  and  mount  a faster   and  stronger  defensive attack ( memory ).  7. Humoral immunity  is provided  by  antibodies  produced  by  B lymphocytes and plasma cells  present  in  the body’s “humors”  or fluids. 8. Cellular immunity  is associated  with   T lymphocytes  and  has living cells as its protective factor. 9.   Adaptive immunity overlaps with innate immunity  [e.g., cytokines released  by the inflammatory   responses  attracts lymphocytes which  in turn  release more cytokines to rev up  the inflammation].  In   particular,  macrophages and dendritic cells play important roles in both innate and adaptive   immunity . B. Antigens  are substances that can mobilize the immune  system  and  provoke  an immune  response. 1.     Complete antigens (immunogens)  are able to stimulate  the proliferation  of specific lymphocytes  and   antibodies, and  to react with  the activated  lymphocytes  and  produced  antibodies.  The most potent   immunogens  are protein  with  molecular weights  above 100,000. 2. Haptens  are molecules that are not immunogenic by themselves but they can react with  specific  antibody.   Haptens  are usually small molecules, but some high-molecular weight  nucleic acids are   haptens  as well.  Many  drugs  such as penicillins are haptens  as are the chemicals in plant  oils that cause   poison  oak or ivy.  Haptens  are not immunogenic because they cannot  activate helper T cells.  The failure   of haptens  to activate is due  to their inability to bind  MHC proteins; they cannot  bind  because they are  
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2422011FallOutlC21Part2 - 21: The Immune System: Innate and...

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