11. Defense

11. Defense - Biology107Fall07 TheBodysDefenses7 1

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Biology 107 – Fall ’07 The Body’s Defenses 7 1 Nonspecific and Specific Defenses Against Infection Reading:  Chapter 43 NON-SPECIFIC DEFENSES (Also Known As INNATE  IMMUNITY) Skin  and  mucous membranes  provide “first line” barriers to infection – “External” defenses o Physical barrier o Secretions/chemicals o Mucus o Gastric acid “Second line” of defense:  - “Internal” defenses o Phagocytes  – Fig. 43.4 – E.g., fixed macrophages in lungs and loose connective tissue o Inflammation  – Fig. 43.6 Characteristics are mediated by  histamine Heat, pain, redness, swelling Histamine – increase in local blood flow, capillaries become leaky o Antimicrobial proteins Complement system  = series of plasma proteins which, when activated, can enhance  inflammation Interferons  Anticancer and antiviral proteins o Fever Pyrogens Endogenous chemicals which induce fever by resetting hypothalamic thermostat In all nonspecific responses, response is same regardless of invading pathogen or trauma. DEFINITION OF SPECIFIC/ACQUIRED  IMMUNITY, AND HOW IT ARISES Two hallmarks of acquired immune responses that differentiate them from the nonspecific responses: o Specificity  – specific lymphocytes “recognize” and respond to specific  antigens o Immunological memory   - long lived memory cells mount a rapid response to second  challenge by the specific antigen Two categories of specific immune responses o Humoral  or  antibody-mediated immunity Involves  B cells  and secretion of protein  antibodies Defends against free bacteria and viruses o Cell-mediated  immunity Involves specific  cytotoxic T cells  which directly kill infected cells Defends against foreign cells  and cells  transformed  by viral infection or cancer The human lymphatic system plays the major roles in the body’s defenses – fig. 43.5
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11. Defense - Biology107Fall07 TheBodysDefenses7 1

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