Slide 1Why is this important?An Overview of the Body’s DefensesHost Defenses: OverviewThe Body’s First Line of DefenseThe Role of Skin in Innate ImmunityThe Role of Mucous Membranes in Innate ImmunityThe Role of the Lacrimal Apparatus in Innate ImmunityThe Role of Normal Microbiota in Innate ImmunityOther First-Line DefensesThe Body’s First Line of DefenseThe Body’s Second Line of DefensePlasmaDefensive Blood Cells: LeukocytesDefensive Blood Cells: LeukocytesGranulocytesAgranulocytesPhagocytosisPhagocytosisChemotaxisAdherenceIngestionPhagosome Maturation and Microbial KillingEliminationPhagocytosisPhagocytosisNonphagocytic KillingNonspecific Chemical Defenses Against PathogensInterferonsType I InterferonsType I InterferonsComplementThe Classical PathwayThe Alternative PathwayThe Lectin PathwayComplementComplementInflammationResults of Acute InflammationDilation and Increased Permeability of Blood VesselsMigration of PhagocytesTissue RepairInflammationSteps of InflammationFeverFeverSummaryM I C R O B I O L O G YWITH DISEASES BY BODY SYSTEM SECOND EDITIONChapter 15Innate Immunity THIRDWhy is this important?•Although we have been around microbes our entire lives, we are actually sick relatively infrequently•Sometimes, the signs and symptoms we feel are actually due our body’s response to the infectionAn Overview of the Body’s Defenses•Species resistance – resistance due to physiological processes of humans that are incompatible with those of the pathogen –Correct chemical receptors not present on human cells–Temperature and pH may be incompatible with those necessary for the pathogen’s survival•We are confronted every day with pathogens that can cause disease–The body must defend itself from these potential pathogens and opportunistic pathogens•Three main lines of defense–First – external physical barriers to pathogens–Second – internal and composed of protective cells, bloodborne chemicals, and processes that inactivate or kill invaders–Third – responds against unique species or strains of pathogensHost Defenses: OverviewThe Body’s First Line of Defense•Made up of structures, chemicals, and processes that work to prevent pathogens entering the body•Includes the skin and mucous membranes of the respiratory, digestive, urinary, and reproductive systemsThe Role of Skin in Innate Immunity•Physical Structure–Epidermis –Multiple layers of tightly packed cells–Few pathogens can penetrate these layers–Shedding of dead skin cells removes attached microbes–Epidermal dendritic cells–Phagocytize pathogens–Dermis–Contains protein fibers called collagen–Give skin strength and pliability to resist abrasions that could introduce microbes•Chemical Substances–Antimicrobial peptides (defensins)–Dermicidins – broad-spectrum antimicrobials–Perspiration contains salt (inhibits growth of and kills pathogens by drawing water osmotically), antimicrobial peptides, and lysozyme (destroys cell wall of bacteria) –Sebum secreted by sebaceous (oil) glands–Helps keep skin pliable and less likely to break or tear–Lowers the pH of the skin to a level inhibitory to many bacteria (pH 5)The Role of Mucous Membranes in Innate Immunity•Cover all body cavities open to the outside environment•Two distinct layers – the epithelium and a deeper connective tissue layer that provides mechanical and nutritive support for the epithelium•Epithelium–Thin, outer covering composed of tightly packed living cells–Continual shedding and replacement of cells carries attached microorganisms away–Dendritic cells phagocytize invaders and “sample” the contents of the interior of the epithelial cells–Sticky mucus that traps microbes–Ciliated columnar cells whose cilia propel mucus –Lysozyme and defensinsThe Role of the Lacrimal Apparatus in Innate Immunity•Group of structures that produce and drain away tears•Tears join the nasal mucus and flow into the pharynx, where they are swallowed•Blinking – spreads tears and washes the surfaces of the eye•Tears contain lysozymeThe Role of Normal Microbiota in Innate Immunity•Normal microbiota help protect the body by competing with potential pathogens (microbial antagonism)•Various activities of the normal microbiota make it hard for pathogens to compete–Consumption of nutrients makes them unavailable to pathogens–Create an environment unfavorable to other microorganisms by changing pH–Help stimulate the body’s second line of defense–Promote overall health by providing vitamins (biotin, B5, folic acid, and a precursor to vitamin K) to hostOther First-Line Defenses•Antimicrobial Peptides (defensins)–Present on skin, mucous membranes, and in neutrophils–Triggered by sugar and protein molecules on the external surfaces of microbes•Other processes and chemicals–Stomach acid – prevents the growth of many potential pathogens–Saliva – contains lysozyme and physically washes microbes from the teethThe Body’s First Line of DefenseThe Body’s Second Line of Defense•Operates when pathogens succeed in penetrating the skin or mucous membranes–Effective against a wide variety of pathogens•Composed of cells, antimicrobial chemicals, and processes but no physical barriers–Many of these components are contained or originate in the blood–Some cells and chemicals from the first line of defense play additional roles in the second line of defensePlasma•Plasma is mostly water containing electrolytes, dissolved gases, nutrients, and proteins–When the clotting factors are removed the remaining fluid is called serum•Includes iron-binding proteins transferrin and ferritin which transport and store iron for humans, but they help sequester iron from microbes–Some bacteria secrete siderophores to steal iron from the body–Body produces lactoferrin–Some bacteria secrete hemolysins which damage RBCs, releasing hemoglobin (contains iron)•Other plasma proteins include complement proteins and antibodiesDefensive Blood Cells: Leukocytes•The cells and cell fragments in plasma are called formed elements•Three types of formed elements–Erythrocytes – carry oxygen and carbon dioxide in the blood–Platelets – involved in blood clotting–Leukocytes (WBC) – involved in defending the body against invaders–Granulocytes – basophils, eosinophils, neutrophils–Agranulocytes – lymphocytes, monocytes, macrophagesDefensive Blood Cells: