The Immune System

1. The Immune System Chapter 43

2. Nonspecific Immunity • Helps prevent the entry of microbes: • Skin and mucus membranes – 1st line of defense • Acidify the skin • Saliva, tears – have antimicrobial proteins • Nostril hairs & mucus • Stomach acids • Helps prevent the spread of microbes: • Phagocytes – destroy themselves and pathogen • Inflammatory response – brings blood and therefore more phagocytes to the area • Antimicrobial proteins – either directly attack microbes or interfere with their reproduction

3. Specific Immunity • The body responds to a particular type of infectious agent • Four components: • Specificity • Diversity • Memory • Self/non-self recognition • Lymphocytes provide the specificity of the immune system

4. Specificity • The immune system is able to recognize and eliminate particular microorganisms and foreign molecules • This is the job of the lymphocytes • Antigen – a foreign substance that elicits a specific response by lymphocytes • Antibody – an antigen-binding protein produced by lymphocytes that functions as the effector in an immune response; these tag the invading cell for destruction

5. Diversity • The ability to respond to the wide variety of antigens which enter the body is based on the diversity of antigen-specific lymphocytes present in the system • The primary immune response is the making of lymphocytes during the 1st exposure to the antigen • A secondary immune response occurs when the body is exposed to the antigen again

6. Memory • The ability to recognize a previously encountered antigen • This is based on memory cells which are produced during the primary immune response • Memory cells are not active during the primary response but survive in the system for a long time • This is acquired immunity

7. Self/non-self recognition • The immune system is able to distinguish between the body’s own molecules and foreign antigens • It develops before birth when the lymphocytes begin to mature • The failure of this ability to recognize self leads to autoimmune disorders that destroy the body’s own tissues

8. Blood groups and transfusion • An example of self/non-self recognition • Type A blood – produces A antigen; makes B antibodies • Type B blood – produces B antigen; makes A antibodies • Type AB blood – produces A and B antigen; makes neither A nor B antibodies • Type O blood – produces neither A nor B antigen; makes both A and B antibodies • Universal donor – Type O: no antigens • Universal recipients – Type AB: no antibodies

9. Immune Response: either humoral or cell-mediated • Humoral immunity – antibodies produced in response to toxins, bacteria, and viruses present in the body fluids (the ‘humors’) • Cell-mediated immunity – the response to intracellular bacteria, viruses, fungi, protozoa, worms, transplanted tissues, and cancer cells

10. Achieving Immunity • Active immunity – conferred by recovery from an infectious disease • Depends on response by the person’s own immune system • May be acquired through illness or vaccination • Passive immunity – transferred from one person to another • Pregnant or nursing mother to child • Artificially from an animal or another person already immune to the disease

11. Abnormal immune function • Allergies – a hypersensitivity to an environmental antigen • Anaphylactic shock – a life-threatening condition associated with some allergens such as insect stings or peanuts; epinephrine may be used as an anecdote • Autoimmune disorders – an immune system reaction against self • lupus erythematous, rheumatoid arthritis, multiple sclerosis, insulin-dependent (‘juvenile’) diabetes -? • Immunodeficiency diseases – immune system is not working • Hodgkin’s disease • AIDS