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Transcript
Immunology Notes Part 3: Immune Response Two types of immune responses: A. Cell-mediated immunity: direct response of T cells to antigens T cells are responsible for cell medicated immunity Killer cells bind to surface of invading cell, disrupt the membrane, and destroy it by altering its internal environment Helper cells stimulate B cells to mature into plasma cells, which begin to synthesize and secrete immunoglobulin (proteins with known antibody activity) Suppressor cells reduce the humoral immunity B. Humoral immunity: also called immunoglobulin-mediated immunity Associated with circulating antibodies B cells are responsible for humoral immunity B lymphocytes enlarge and divide to become mature plasma cells. The plasma cells secrete antibodies into blood and lymph Five classes of immunoglobulin: Functions: 1. Neutralization: masks dangerous parts of bacterial exotoxins, viruses 2. Agglutination : mismatched blood 3. Precipitation IgG: makes up about 80% of plasma antibodies. It appears in all body fluids and is the major antibacterial and antiviral antibody. Only one to cross placenta IgM: is the first immunoglobulin produced during an immune response. It’s too large to easily cross membrane barriers and is usually present on in the vascular system. IgA: found mainly in body secretions, such as saliva, sweat, tears, mucus, bile, and colostrums. It defends against pathogens on body surfaces, especially those that enter the respiratory and GI tracts. IgD: is present in plasma and is easily broke down, It’s the predominant antibody on the surface of B cells and is mainly an antigen receptor. IgE: the antibody involved in immediate hypersensitivity reactions, or allergic reactions that develop within minutes of exposure to an antigen. IgE stimulates the release of mast cell granules, which contain histamine and heparin. Almost never in blood. Complement system: part of the humoral immunity. It is the major mediator of the inflammatory response and consists of 20 proteins circulating as functionally inactive molecules. System causes inflammation by increasing: a. vascular permeability b. chemostasis c. phagocytosis d. lysis of foreign cell --------------------------------------------------------------------------------------------------------------------First Line of Defense: A. Intact Skin/Epidermis: forms mechanical barrier that prevents entry of pathogens and other harmful substances into the body. 1. Acid mantle: skin secretions (perspiration, sebum) make epidermal surface acidic which inhibits bacterial growth; sebum contains bactericidal chemicals 2. Keratin: provides resistance against acids, alkalis, and bacterial enzymes B. Intact Mucous Membranes: form mechanical barrier that prevents entry of pathogens 1. Mucus: traps microorganisms in respiratory and digestive tracts 2. Nasal hairs: filter and trap microorganisms in nasal passages 3. Cilia: propel debris-laden mucus away from lower respiratory tract 4. Gastric juice: contains concentrated HCl and protein digesting enzymes that destroy pathogens in the stomach 5. Acid mantel of vagina: inhibits growth of bacteria and fungi in female reproductive tract 6. Lacrimal secretions (tears)/saliva: continuously lubricate and cleanse eyes (tears) and oral cavity (saliva); contain lysozyme (enzyme that destroys microorganisms) 7. Urine: normally acid pH inhibits growth; cleanses lower urinary tract as it flushes from the body. Second Line of Defense: Nonspecific Cellular and Chemical Defenses A. Phagocytes: engulf and destroy pathogens that breach surface membrane barriers; macrophages also contribute to immune response B. Natural Killer cells: promote cell lysis by direct cell attack against virus-infected or cancerous body cells; do not depend on specific antigen recognition. C. Inflammatory Response: prevents spread of injurious agents to adjacent tissues, disposes of pathogens and dead tissue cells, promotes tissue repair: chemical mediators released attract phagocytes (and immunocompetent cells) to the area. 1. Inflammatory chemicals: a. Histamine: from granules of basophils; released in response to mechanical injury, presence of certain microbes, and chemicals released by neutrophils; promotes vasodilation of local arterioles, increases permeability of local capillaries – permits exudates formation b. Kinins (bradykinin, etc.): peptide formed from plasma protein found in plasma, urine, saliva, lysosomes of some neutrophils and other cells. c. Prostaglandins: fatty acid molecule found in all cell membranes; generated by lysosomal enzymes of neutrophils and other cells; sensitize blood vessels to effects of other inflammatory mediators 2. Four cardinal signs: redness, heat, swelling, pain (might also include impairment of function) 3. Hyperemia: congestion with blood 4. Exudate: fluid containing proteins such as clotting factors and antibodies 5. Pus: mixture of dead or dying neurtophils, broken down tissue cells, and living and dead pathogens 6. Abcess: inflammatory mechanism fails to clear area of debris; sac of pus walled off by collagen fibers; surgical draining often needed before healing occurs D. Antimicrobial Proteins 1. Interferons: proteins released by virus-infected cells that protect uninfected tissue cells from viral takeover; mobilizes the immune system 2. Complement: lysis microorganisms, enhances phagocytosis, intensifies inflammatory and immune responses. E. Fever: systemic response initiated by pyrogens; high body temperature inhibits microbial multiplication and enhances body repair processes Third Line of Defense: Specific Body Defenses, Immune Response