<aside> 💡 Intro to Immunology and Vaccination

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• LO1 compare and contrast the innate and adaptive immune defence systems

  • Immune response to infection

    • Local infection, penetration of epithelium
      • Wound healing induced
      • Antimicrobial proteins
      • Phagocytes
      • Activation of complement
    • Local infection of tissues
      • Activation of complement
      • Dendritic cells which phagocytised pathogens migrate to lymph nodes
      • Phagocyte activation of adaptive immune response
      • NK cells activated
      • Cytokine and chemokines produced

  • Innate (nonspecific) defence system

    • First line of defense: external body membranes (skin, mucosae)
    • Second line of defense: antimicrobial proteins, phagocytes, and other cells
    • Present at birth
    • Attempts to immediately destroy pathogen
    • Contains infection until more powerful adaptive immune system adapts
    • Always present
    • Immediate
    • low potency general response
      • Reacts with equal potency upon repeated exposure to same pathogen
    • General protection against a wide range of pathogens
    • Wide variety of body responses
    • Protect against invasion of a wide variety of pathogens/toxins
    • Born with this kind of immunity
    • Essential for rapid response against microbes
    • React essentially in the same way to repeat infection

    • Physical/Mechanical defenses

      • Skin (forms physical barrier to entry of microbes)
      • Mucous membranes: inhibits entrance of many microbes, not effective as intact skin
      • Tears/liminal apparatus: dilute and wash away irritating substances
      • Saliva: washes microbes from teeth and mouth
      • Mucus: traps microbes in respiratory and GIT
      • Cilia: together with mucous, traps and remove microbes and dust from URI
      • Nasal hair: filter out dust and microbes in nose
      • Epiglottis
      • Urine flow: washes microbes from urethra
      • Defecating: expels microbes from body
      • Vomiting: violent expulsion of stomach contents

    • Chemical defences

      • Sebum: oily, acidic antimicrobial secretion of the sebaceous glands
      • Lysozyme: enzyme cleaves peptidoglycan cell wall; sweat, tears, saliva, nasal secretions, tissue fluids
      • Vaginal secretions: slightly acidic, discourages bacterial growth, flushes microbes out of vagina
      • Gastric juice: acidity destroys bacteria and toxins

    • Internal defences

      • Antimicrobial proteins
        • Interferons: protect uninfected host cells from viral infections
        • Complement system: cytolysis of microbes, phagocytosis, inflammation
        • Iron binding proteins: limits iron required for bacterial growth
        • Antimicrobial proteins: broad spectrum antimicrobial activities, chemotaxis of dendritic and mast cells
      • Phagocytic cells
        • Phagocytic (neutrophils & macrophages): ingest foreign matter
        • Natural killer (NK) cells: kill infected target cells by releasing perforin and granzymes granules; phagocytes then kill released microbes
      • Innate Processes
        • Fever (intensifies effects of interferons, inhibits microbial growth, speeds up reactions that aid repair)
        • Inflammation (confines and destroys microbes, initiate tissue repair)

    • Phagocytosis

      • Chemotaxis to pathogen by chemical stimulus
      • Pathogens adhere to phagocyte cell membrane
      • Phagocyte develops pseudopods
      • Phagocytes endocytoses pathogen into phagosome
      • Pathogen enclosed in vesicle merges with lysosomes (phagolysosome)
      • Digestive enzymes break down pathogens
      • Results in a phagolysosome with residual bodies from digestion

      

    • Inflammation

      • In response to tissue injury or infection
      • Increased capillary permeability
      • Phagocytes emigrate by chemotaxis to site of injury

  • Adaptive immunity

    • Ability of the body to defend itself against specific invading agents
    • Specificity and memory
    • Needs to be activated; normally inactive
    • Slower (1-2 weeks)
    • Response varies
    • Enables faster, stronger secondary response
    • Highly potent
    • Responses are highly evolved
    • Stimulated by exposure to the infectious agent and increase in magnitude
    • Depending on the microbe adaptive immune response either humoral or cell-mediated
    • Lymphocytes major components
      • Third line of defence attacks particular foreign substances
      • Takes longer to react than innate
      • Activation of specific lymphocytes
      • Combats a particular pathogen or other foreign substance

  • Phases of adaptive immunity

• LO2 outline the various white blood cell types and their basic functions
• LO3 describe the major organs of the lymphatic system and their basic role in the immune system
• LO4 describe the various components of the two lines of innate defence, and describe their roles
• LO5 compare and contrast the 2 types of adaptive immunity – humoral v cell-mediated
• LO6 define antigens, and describe the main pathways for antigen processing
• LO7 compare and contrast the general function of T and B lymphocytes
• LO8 define immunological memory
• LO9 compare naturally v artificially acquired immunity, and active v passive immunity
• LO10 outline the different types of vaccines and vaccine constituents
• LO11 discuss issues associated with vaccination and anti-vaccination campaigns