immune system

• Body's defense systems


  • Immune System
  • Innate (nonspecific) defense system
  • Adaptive (specific) defense system
• Innate (nonspecific) defense system


  • Mechanisms protect against a variety of invaders
  • Respond immediately to protect body from foreign materials
• Adaptive (specific) defense system


  • Specific defense is required for each type of invader (pathogen)
• Innate defense system (mechanical defenses)

  1. First line of defense-Covering and Mucous Membranes

  2. Second line of defense-Cells and Chemicals (Internal Defenses)
• First line of defense-Covering and Mucous Membranes

  • Bodily coverings-fine line of defense
  • Physical barriers to foreign materials
  • Provides protective secretions
• Ph of skin is acidic so it can inhibit bacterial growth
• Sebum is toxic to bacteria
• Stomach secretions and saliva secretions are very acidic
• Mucous membranes


  • First line of defense
  • Stomach mucus secretes HCl
  • Has protein digesting enzymes
• Salive and lacrimal fluid (tears) contain lysozymes-enzyme that destroys bacteria
• Mucus traps microorganisms in digestive and respiratory pathways
• Second line of defense-Cells and Chemicals (Internal Defenses)

  • Phagocytes (cells such as neutrophils, macrophages and dendritic cells)
  • Engulf foreign materials into vacuole
  • Enzymes from lysosomes digest the material
• Neutrophils


  • The Bacteria Slayer
  • Arrive to the infected site via diapedesis
  • Work so hard that they end up killing themselves after killing bacteria
• Lysosomes


  Organelles that contain hydrolytic enzymes
• Respiratory burst in neutrophils

  Produce hydrogen peroxide
• Dead neutrophils are a major part of pus
• Big Eater Macrophage


  Phagocytic cells that continue to eat bacteria
• Phagocytosis occurs within the cells called neutrophils dendritic cells as well as macrophages
• Immune response to infection

  1. Cytotoxic T cells kill infected/cancerous cells

  2. Helper T cells activate B cells to produce antibodies

  3. Memory T cells respond faster to future infections

  4. Regulatory T cells suppress immune response
• Natural Killer Cells


  Large granular lymphocytes that attack cells lacking "self" cell-surface receptors (MHC)
• Natural Killer Cell killing

  1. Bind to infected cell

  2. Create pore in cell membrane

  3. Release granzyme to induce apoptosis
• Signs of Inflammation

  Redness, heat, swelling, and pain( temporary loss of joint movement and faster metabolic rate for tissue cells)
• functions of inflammatory response

  1. Triggered by tissue injury

  2. Prevents spread of damaging agents

  3. Sets stage for repair
• Neutrophil response to infection

  1. Arrive at site via diapedesis and chemotaxis

  2. Consume foreign material
• Complement system


  Group of 20 plasma proteins that damage foreign cell surfaces
• Complement Proteins

  1. Activated when they attached to cells (complement fixation)

  2. Cause opsonization by releasing vasodilators and chemotaxis chemicals and opsonization enhances their recognition to phagocytes can grab the bacteria faster
• Interferons


  Cytokines secreted by virus-infected cells that bind to healthy cells to interfere with viral replication
• hypothalamus heat regulation can be reset by pyrogens which are secreted by WBC’s
• 3 Aspects of adaptive defense

  • Recognizes and acts on specific foreign substances (antigens specific)
  • Pathogens encountered in one part of the body can be effectively targeted and eliminated by immune cells located elsewhere ( systemic) Recognizes and creates a stronger attack if there is a second exposure (memory)
• Types of immune responses

  • Humoral (antibody-mediated)
  • Cellular (cell-mediated)
• Antigens


  Substances that can trigger an immune response, including proteins, nucleic acids, carbohydrates, lipids, and microorganisms
• Self-antigens


  Surface proteins on our own cells that the immune system does not attack
• Allergens


  Substances that trigger harmful immune responses in allergic individuals
• MHC I and MHC II

  Important for T cell activation, display self and foreign proteins respectively
• Cell of Adaptive define system

  • Lymphocytes respond to specific antigens
  • Macrophages, Dendritic cells and B cells help lymphocytes (not really 8, when t activated it helps B, so not B cells)
  • They are MHC II-Antigen Presenting Cells
  • Immunocompetent
  • They present a portion of the peosin of the pathogen they have phagocytised to T cells (the correct immunocompetent T call)
• When a cell becomes capable of responding to a specific antigen by binding to it becomes what....Immunocompetent
• Most never really get exposed so their specific antigen and remain naive
• Antigen Receptor Diversity


  • Genes determine which foreign substances the immune system will recognize
  • These pine are shuffled by somatic recombination
• Part of both in and adaptive Macrophages

  • Antigen presenting calls and are widely distributed in lymphoid organs
• Positive Selection Process


  • Developing B cells generate functional antigen receptors that are capable of recognizing a wide range of potential antigens encountered in the body
  • Those that are self-reactive are eliminated by apoptosis (Hamacal Libby-mediated)