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IUPUI MICR J210 - Overview of the Body's Defenses

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MICR J210 1st Edition Lecture 7Outline of Current Lecture 1. Overview of the Body’s Defenses2. General Mechanisms of the Immune System3. Normal Microbiota in Innate Immunity4. Defense Components of Blood5. Phagocytosis6. Nonphagocytic Killing7. The Complement Cascade8. Inflammation9. FeverCurrent LectureOverview of the Body’s Defenseso Resistance to most plant and animal pathogenso Species resistance Due to physiological processes of humans that are incompatible with those of the pathogen- Correct chemical receptors not present on human cellso Conditions may be incompatible with those needed for pathogen’s survivalo Immune system-helps protect against cancerous cells, pathogens, toxins, and dead cells or pollutiono Protects us from a variety of human pathogenic agents;o Innate: the immunity that you’re born withGeneral Mechanisms of the immune system: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.- Nonspecific mechanisms (innate)o Rapid response within hourso Fixedo Limited number of specificitieso Constant during responseo Hardwired, built into the DNA Recognizes that there is a problem and recruits the acquired immunity to help Constant during responses- Specific mechanisms (acquired) o Slow response within days to weekso Variableo Numerous highly selective specificitieso Improve during response (through memory cells)o Not coded in the DNA—has to be developed over time- Defenseso First line of defense: skin, mucosa (barriers) Structures, chemicals, and processes that work to prevent pathogens entering the body- Skino The Role of Skin in Innate Immunity Skin composed of two major layers- Epidermis o Multiple layers of tightly packed cellso Few pathogens can penetrate these layerso Shedding of dead skin cells removesmicroorganismso Epidermal dendritic cells phagocytize pathogens- Dermiso Collagen fibers help skin resist abrasions that could introduce microorganisms Skin has chemicals that defend against pathogens- Perspiration secreted by sweat glands- Salt inhibits growth of pathogens- Antimicrobial peptides act against microorganisms- Lysozyme destroys cell wall of Gram (+) bacteria - Sebum secreted by sebaceous (oil) glands- Helps keep skin pliable and less likely to break or tear- Lowers skin pH to a level inhibitory to many bacteria- Mucous membranes of the respiratory, digestive, urinary, and reproductive systems Mucous membranes line all body cavities open to environmento Two distinct layers Epithelium- Thin, outer covering of the mucous membranes- Epithelial cells are living- Tightly packed to prevent entry of pathogens- Continual shedding of cells carries away microorganisms Deeper connective layer that supports the epitheliumo Phagocytosis: eat the entire cello Inflammation: recruitment of phagocytes to site of infectionso Complement: proteins floating around in bloodo Humoral immunity: B lymphocytes (soluble antibodies) dissolved in the bloodo Cell-mediated: T cells –cytotoxic t cellso Antigen processing and presentation: communication between innate and adaptive- Lacrimal apparatuso Produces and drains tearso Blinking spreads tears and washes surface of the eyeo Lysozyme in tears destroys Gram (+) bacteriaNormal Microbiota in Innate Immunity (digestive system)• Microbial antagonismo Normal microbiota compete with potential pathogens- Activities of normal microbiota make it hard for pathogens to competeo Consumption of nutrientso Create an environment unfavorable to other microorganisms Commensals compete with pathogens: need enough space and nutrientso Help stimulate the body’s second line of defenseo Promote overall health by providing vitamins to hosto Help us digest certain nutrientso Help keep immune system in check Beneficial functionOther First-Line Defenses• Antimicrobial peptidesPresent in skin, mucous membranes, neutrophilsAct against a variety of microbesWork in several waysInducing holes in bacterial membranesIntracellular killing• Other processes and chemicalsMany organs secrete chemicals with antimicrobial properties• Operates when pathogens penetrate the skin or mucous membranes• Composed of cells, antimicrobial chemicalsMany of these components are contained or originate in the bloodPhagocytic cells (blood and tissues)Nonspecific Chemical Defenses Against Pathogens• Complement proteins (serum)• Antimicrobial peptides (all body secretions)• Interferons (3 types)Inflammation• feverDefense Components of Blood• Plasma: the liquid part of blood• Serum: same as plasma just no clotting factors…they are all in the blood clot at the bottom of the tube• Defense Components of Blood• Cells and cell fragments in plasma are called formed elementso Three types of formed elements (blood cells and platelets) Erythrocytes- Carry oxygen and carbon dioxide in the blood Platelets- Involved in blood clotting Leukocytes (white blood cells)- Involved in defending the body against invaders- Divided into granulocytes and agranulocyteso Granulocytes; Contain large granules that stain different colors Three types- Basophils – stain blue with basic dye methylene blue- Eosinophils – stain red/orange with acidic dye eosin- Neutrophils – stain lilac with mix of acidic and basic dyes Neutrophils and eosinophils- Phagocytize pathogens- Capable of diapedesis (Chemotaxis)o Agranulocytes Cytoplasm appears uniform under a light microscope Two types- Lymphocyteso Most involved in adaptive immunity- Monocyteso Leave the blood and mature into macrophages• Lab analysis of leukocyteso Differential white blood cell count can signal signs of disease Increased eosinophils indicate allergies or parasitic worm infection Bacterial diseases often show increase in leukocytes which are mostly neutrophils Viral infections show increase in lymphocytesPhagocytosis• Phagocytosis• Cells capable of phagocytosis are called phagocytes• Phagocytosis is not completely understood• Can be divided into six stageso Chemotaxis  Aided by the inflammatory responseo Adherenceo Ingestion (in phagosome)o Fusion with lysosome Known as a phagolysosome when the phagosome is fused with the lysozymeo Killing o Elimination• Nonphagocytic Killingo Killing by eosinophils Attack parasitic helminths by attaching to their surface- Secrete toxins that weaken or kill the helminth- Eosinophilia


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IUPUI MICR J210 - Overview of the Body's Defenses

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