microbio- chapter 15

microbio- chapter 15 - Chapter 15 Overview of the Innate...

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Chapter 15 Overview of the Innate Defenses 1. First line defenses are barriers that separate and shield the interior of the body from the surrounding environment 2. Two groups of sensors: o Toll like receptors o NOD o Recognize families of compounds unique to microbes, enabling the cell to sense invaders and then send chemical signals to alert other components of the host's defense o Another sensor is the complement system (a series of proteins always present in blood and tissue fluids) 3. A cytokine produced by one cell diffuses to another and binds to the appropriate cytokine receptor of that cell. When a cytokine binds a receptor, a signal is transmitted to the interior of the cell, inducing certain changes in the activities of the cell First-Line Defenses 4. Physical barriers such as the skin and mucous membranes, and the antimicrobial substances in secretions that bathe those barriers 5. Normal microbiota helps prevent harmful microbes from colonizing the body surfaces 6. Physical Barriers o Skin Dermis contains tightly woven fibrous connective tissue, making it extremely tough and durable Epidermis is composed of many layers of epithelial cells that become progressively flattened toward the exterior The cells continually slough off, taking with them any microbes that might be adhering o Mucous Mmbranes Line the digestive tract, respiratory tract, and genitourinary tract Some mucous membranes have mechanisms that propel microbes, directing them toward areas where they can be eliminated more easily (ex: urine, peristalsis) Cilia constantly beat in an upward motion propelling materials away from the lungs to the throat 7. Antimicrobial Substances o Sweat : high in salt, as it evaporates it leaves a salty residue, inhibiting many organisms that might otherwise proliferate on the skin o Lysozyme : enzyme that degrades peptidoglycan; found in tears, saliva, and in mucus; also found in phagocytic cells, blood, and the fluid that bathes tissues o Peroxidase enzymes: found in saliva, milk, body tissues, and inside phagocytes; break down hydrogen peroxide and produce potent oxidizing compounds Bacteria that produce catalase may avoid the damaging prodcuts associated with peroxidase activity o Lactoferrin: iron-binding protein found in saliva, mucus, and milk. A similar compound transferrin is found in blood and tissue fluids. Iron is a major element
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required for growth of many microorganisms; some bacteria make compounds that capture iron from the host, however o Defensins: short antimicrobial peptides produced by neutrophils and epithelial cells; they function by inserting into bacterial membranes, forming pores that disrupt the integrity of the cell 8. Normal Microbiota (Flora) o Competitive exclusion of pathogens (ex: cover binding sites, consuming nutrients, etc) o Produce compounds toxic to other bacteria o Essential to the development of the immune system in infants The Cells of the Immune System: 9. Hematopoiesis: formation and development of blood cells
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This note was uploaded on 09/16/2009 for the course MICR 255 taught by Professor Kramer during the Spring '07 term at UNC.

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microbio- chapter 15 - Chapter 15 Overview of the Innate...

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