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UIUC MCB 100 - Ch. 15: Nonspecific Host Defenses

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MCB 100 1st Edition Lecture 41 Outline of Last Lecture I. Infection vs. diseaseII. Stages of an infectious diseaseIII. Portals of entryIV. Opportunistic vs. true pathogens V. Virulence and virulence factors Outline of Current Lecture I. Resistance and immunity II. Host defenses against pathogens III. Physical and chemical barriers Current LectureI. Resistance and immunitya. Resistance: the natural ability of a host to resist an infection by a microorganism thatthe host has never encountered before; relies on nonspecific defensesb. Immunity: an enhanced resistance to a specific infectious agent that arises in a host as a result of previous exposure to that infectious agent; the immune response involves the production of specific proteins called antibodies that target defense responses against the specific pathogen c. Conditions that can cause a persons resistance to disease to be reduced: i. Old age ii. Very young ageiii. Starvationiv. Heredityv. Climatevi. Povertyvii. Stressviii. Cuts and open soresix. Hospitalizationx. AIDSxi. Cancerxii. Immunosuppressant drugsxiii. SurgeryII. Host defenses against pathogens a. 1st line:These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.i. Physical and chemical barriers on the surface of the bodyii. Skin, mucous membranes, chemicals, lysozyme, defensins (small antimicrobial proteins that are found in saliva, sweat, and sebum) a. 2nd line: i. Defenses that are found inside the body that can inhibit or kill a microorganism that the host has never before encountered ii. Always present inside the bodyiii. Phagocytosis, complement when it is activated by the alternative or properidin pathway, interferon, inflammation, feveriv. Phagocytes: 1. cell that can engulf and devour microorganisms 2. Move around in body searching for foreign objects like bacteria and eat them 3. Phagocytes play a role in resistance in that they can recognize and destroyinvading bacteria in a nonspecific way4. Play a role in immunity when they work with antibodies to destroy specific bacteria5. Major types:a. Monocytes: leukocytes with a large round nucleus that develop intomacrophages b. Macrophages: found in various parts of the body- blood, lymph nodes, epithelial layers, mucous membranesc. Dendrite cells: found in intestinal walls, the thymus, and other placesd. Kupffer cells: macrophages in the livere. Microglial cells: macrophages that are seen in the brainf. Neutrophils: most common polymorphonuclear leukocyte (PMN) i. Leukocytes1. White blood cells; major player in the body's defense against infection2. Two major categories:a. Lymphocytes: non-phagocytic, involved in specific immune responsesb. Phagocytes: engulf and digest bacteria, yeasts, and small protozoa i. Complement:1. Complement system is a group of about 20 different proteins found in blood serum that play a role in destroying infectious microorganisms2. Some complement proteins bind to bacteria and other microorganisms and act as opsonins, others are cytokines or chemotactic factors and some form the membrane attack complex 3. Circulate in the blood in an inactive form and are activated by enzymes that cleave off block groups4. Can also be activated by antibodies- part of the specific immune responseto a previously encountered pathogena. 3rd line:i. Specific defenses; specific immune response is not active until after the host has encountered a pathogenii. Lymphocytes, antibodies made by B-lymphocytes), cytotoxic T-Cells, complement when it is activated by classical/antibody-dependent pathwayII. Physical and chemical barriersa. Skin: a physical and mechanical barrier; provides some chemical barriers against microbial infectioni. Enzymes in sweat degrade bacterial cell walls ii. Defensins: small antimicrobial peptides iii. Organic acids lower pHiv. High levels of salt are caused by the evaporation of sweatv. These factors inhibit microbial growth. Microorganisms that survive well on theskin as normal flora are usually not well adapted to infect deeper tissues b. Respiratory tract:i. Upper respiratory tract is lined with mucosal epitheliumii. This type of tissue produces a sticky substance called mucous that can trap microorganisms and contains a lot of antibodiesiii. The mucosal epithelium is also covered with tiny hair-like projections called cilia that move the bacteria that get trapped in the mucous towards the digestive


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UIUC MCB 100 - Ch. 15: Nonspecific Host Defenses

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