Chapter 15Innate (Nonspecific) Immunity Why 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 to our body's response to the infection An Overview of the Body's Defenses-Species resistance: resistance due to the cells and physiological processes of humans that are incompatible with those of most plant an animal pathogensoCorrect chemical receptors not present on human cellsoTemperature and pH may be incompatible with those necessary for the pathogen's survival-We are confronted every day with pathogens that can cause disease-Three main lines of defenseoFirst: external physical barriers to pathogens (skin and mucous membranes)oSecond: internal and composed of protective cells, blood-bourne chemicals, and processes that inactivate or kill invadersoThird: responds against unique species or strains of pathogens An Overview of the Body's Defenses VIDEO-Defenses act together to protect body-First- NonspecifcoSkin and mucous membranes-Second- NonspecificoPhagocytosisoComplement system-Third- SpecificoActivated by antigen specific cells-Antibodies -Cytotoxic cells The 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 systems-First line can be classified as oStructural-Skin and mucous membrane-More organisms are able to infect mucous membranes because of the warmth and live nature oMechanical-Cilia, urine, defecation, etc: clears body outoBiochemical The Role of Skin in Innate Immunity-Physical Structure - Structural oEpidermis-Multiple layers of tightly packed cellsFew pathogens can penetrate these layers-Shedding of dead skin cells removes attached microbes-Epidermal dendritic cellsNonspecifically phagocytize pathogensLive in epidermisoDermis-Contains protein fibers called collagenGive skin strength and pliability to resist abrasions that could introduce microbes-Be poked by something and not have a big tear in our skin-Chemical Substances - Biochemical oAntimicrobial peptides (defensins)oDermicidins: broad spectrum antimicrobialsoPerspiration contains salt (inhibits growth of and kills pathogens by drawing water osmotically - hypertonic solution), antimicrobial peptides, and lysozyme (destroys cell wall of bacteria)oSebum 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 of the environment-Two distinct layers: the epithelium and a deeper connective tissue layer that provides mechanical and nutritive support for the epithelium-EpitheliumoThin, outer covering composed of tightly packed living cellsoContinual shedding and replacement of cells carries attached microorganisms awayoDendritic cells phagocytize invaders and extend pseudopods between epithelial cells to "sample" contents of the lumen oSticky mucous that traps microbesoMechanical: Ciliated columnar cells whose cilia propel mucous and trapped particlesoBiochemical: Lysozyme and defensins-Lysozyme: destroys peptidoglycan of cell walls (of bacteria)Found in tears, saliva, etc. The Role of the Lacrimal Apparatus in Innate Immunity-Group of structures that produce and drain away tears-Tears join the nasal mucous and flow into the pharynx, where they are swallowed-Mechanical: Blinking: spreads tears and washes the surfaces of the eye-Tears contain lysozyme The 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 competeoConsumption of nutrients makes them unavailable to pathogensoCreate an environment unfavorable to other microorganisms by changing pHoHelp stimulate the body's second line of defenseoPromote overall health by providing vitamins (biotin, B5, folic acid, and a precursor to vitamin K) to host Other First-Line Defenses-Antimicrobial Peptides (defensins)oPresent on skin, mucous membranes, and in neutrophilsoTriggered by sugar and protein molecules on the external surfaces of microbes-Other Processes and ChemicalsoStomach acid: prevents the growth of many potential pathogens, pH ~2oSaliva: contains lysozyme and physically washes microbes from the teeth The Body's Second Line of Defense-Operates when pathogens succeed in penetrating the skin or mucous membranes (first line of defense)oEffective against a wide variety of pathogens-Composed of cells, antimicrobial chemicals, and processes, but no physical barriers (skin and mucous membranes) oMany of these components are contained or originate in the bloodoSome cells and chemicals from the first line of defense play additional roles in the second line of defense Defensive Components of Blood-PlasmaoLiquid component of blood (~55% of blood)oIncludes 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Strip iron from transferrin and ferritin-Body produces lactoferrin which strips iron from siderophores - greatest affinity to ironoOther plasma proteins include complement proteins and antibodies-Defensive Blood Cells: LeukocytesoThree types of formed elements-Erythrocytes (RBC): carry oxygen and remove carbon dioxide in the blood-Platelets: involved in blood clotting-Leukocytes (WBC): involved in defending the body against invadersNever Let Monkeys Eat BananasGranulocytes-Basophils-Eosinophils-NeutrophilsAgranulocytes-Lymphocytes-Monocytes-Macrophages Defensive Blood Cells: LeukocytesGranulocytes-Contain large granules that stain different colors-BasophilsoNot phagocyticoCan migrate from bloodstream into tissueoRelease inflammatory chemicals which influence the tone and diameter of bloodvessels-EosinophilsoPhagocyticoCan migrate from the bloodstream into tissueoDefend against parasitic wormsoPlay a role in allergic reactions-Neutrophils (PMNs)oDark staining area on pictureoLobes on nucleioPhagocyticoRapidly move from bloodstream into tissue-EbolaoStart with monocytes (in turn then macrophages) then destroy neutrophilsoLytic cycle