1、1,Chapter 14 Talaro,The Nature of Host Defenses Nonspecific Defense,2,Defenses can be classified as either (1) innate & nonspecific or (2) acquired & specific,3,1st Line of Defense Physical / anatomical barriers Chemical barriers Innate /genetic barriers 2nd Line of Defense Phagocytic white blood ce
2、lls Inflammation - Complement proteins Fever - Interferon 3rd Line of Defense B cells Antibodies T cells Specific - acquired Killer cells,Nonspecific - innate,4,Physical or Anatomical Barriers,Outermost layer of skin Epithelial cells Compacted, cemented together & impregnated with keratin Damaged ce
3、lls are rapidly replaced Sweat glands Flushing effect Mucous membranes Impedes attachment & entry of bacteria- also keeps membranes moist Blinking & tear production also keeps surfaces moist Nasal hair traps larger particles Ciliated epithelial cells in upper respiratory tract keeps moving small obj
4、ects out on a continual basis. (“ciliated escalator”),5,Chemical Defenses,Sebaceous secretions sebum and dead cells Inhibit attachment of bacteria also lysozyme, phospholipase 2 amd lactoferrin Acidic pH of vagina normal flora like Lactobacillus Urine correlated with high concentrations of urea and
5、ammonia,6,Physical & Chemical Barriers,General protection mechanisms that attempt to stop pathogens from invading the body.Evidence for the effectiveness of physical & chemical barriers can be deduced by observing individuals who have lost or never had them.,7,Genetic Defenses,Some hosts are genetic
6、ally immune to the diseases of other hosts Some pathogens have great specificity Some pathogens have a narrow host range,“Humans cant acquire distemperfrom cats & cats cant getmumps from humans.”Foundations in Microbiology (5th) Talaro,“Shigella are pathogens of humans and baboons but notchimpanzees
7、.” Todars On-Line Textbook of Bacteriology,Why?,Possible ExplanationsAbsence of receptor on host cellAbsence of a particular cell or tissueInappropriate temperature for growthMissing nutritional requirementMissing target for toxin,Age, sex, stress, diet/malnutrition, trauma or other disease may pred
8、ispose the host to infection. Todars On-Line Textbook of Bacteriology,8,The Second Line of Host Defense,Second line of defense is much more complex,involves many different types of cells, many levelsPhagocytosisInflammation redness and increased blood flow and increase in temperature, edema Fever in
9、crease in temperature of bodyComplement proteins,9,Immunology: the study of the immune system,Surveillance of the body Immune cells constantly move throughout the body searching for pathogens & infected / damaged cells Recognition of foreign material Self versus non-self Glycoproteins Destruction of
10、 foreign entities or infected/damaged cells Phagocytosis Induce apotopsis Programmed Cell Death,Immune system is responsible for,10,Epitope,Ab recognize and bind to a specific epitope,Proteins produced by the immune system that specifically binds to an epitope and initiates its removal of the antige
11、n from the body,Some more definitions,11,Specialized WBC “touch” cells as they pass through tissues. The WBC recognize surface glycoproteins to determine what is self and what is not. An immune response is mounted if non-self glycoproteins are recognized.,12,Human Body & the Immune System Network of
12、 cells & fluids that permeate every organ & tissue Fluid-filled spaces that are interconnected,Reticuloendothelial System (RES) Very important part of immune system consists of monocytes and macrophages Fibrous support network enmeshing cells reticular connective tissue This web connects one cell to
13、 another within a tissue or organ and provides a niche for phagocytic WBC Reticulum = small net Endothelium = lining of a blood vessel Extracellular fluid (ECF) Spaces surrounding tissue cells Bloodstream Lymphatic System A system of vessels & organs that serve as sites for the development of immune
14、 cells Spleen, thymus, lymph nodes & gut-associated lymphoid tissue,13,Dendritic Cells An antigen-presenting leukocyte that is found in the skin, mucosa, and lymphoid tissues and that initiates a primary immune response.,Neutrophil Cell An abundant type of granular white blood cell that is highly de
15、structive of microorganisms.,Macrophage Large phagocytic cells found in the reticuloendothelial system,Reticuloendothelial System,14,Leukocytes or WBC Classified according to staining reactions: Granulocytes: granules in the cytoplasm & lobed nucleus Agranulocytes: smaller granules & round nucleus,N
16、eutrophils or polymorphonuclear (PMNs) Phagocytes in tissue make up 55 to 90% of circulating leukocytes (25 billion cells) live for about 8 days Eosinophils Destroy eukaryotic pathogens such as Helminth worms & fungi 1-3% of total WBC Basophils Destroy eukaryotic pathogens - 0.5% of circulating WBC
17、Mast Cells Granules containing histamine & heparin Histamine dilates blood vessels and makes their walls permeable Heparin inhibits blood clotting Mucous membranes & connective tissue,Granulocytes,15,Neutrophil,Eosinophils,Basophil,Mast cell,Polymorphonuclear,16,Process in which phagocytes engulf an
18、d digest microorganisms and other cellular debris,What is phagocytosis?,Lysozymes fuse and release digestive enzymes and reactive oxygen compounds,An important defense against infection,Bacterial cells,Pseudopodium,17,Agranulocytes,Lymphocytes - 20-35% of circ. WBC B cells mature in bone marrow T ce
19、lls mature in thymus Involved in the specific immune response Monocytes largest of all WBC (3-7%) Phagocytic Differentiate into macrophages Found in tissue Consume damaged host cells Present antigens Regulation of the immune systems Differentiate into dendritic cells Trap pathogens in the lymphatic
20、tissue Present antigens Also important in specific immune response,T cell,Infected cell,18,Vasoconstriction,histamine & heparin,Vasodilation,Edema Infiltration of neutrophils Eliminate microbes, particulate matter & dead or injured cells Extract antigens,Macrophages & Lymphocytes Macrophages = phago
21、cytosis B cells = antibodies T cell = killer & memory cells,Inflammatory Response,19,Tissue Repair,Involves replacement of dead or damaged cellsBegins during active phase of inflammationExtent of regeneration depends on tissue type, requires production of new cells by STROMA (supportive connective t
22、issue) or PARENCHYMA (active part of tissue)Parenchymal regeneration restores skin to original form,Stromal regeneration resultsin scaring,20,Fever,Systemic nonspecific response to infection Higher than normal body temperaturePyrogenExogenousLPS, pathogens, foreign cells, vaccinesEndogenousInterleuk
23、in-1 (IL-1) & Tumor necrosis factor (TNF)Monocytes, neutrophils & macrophagesResets hypothalamus (in brain) thermostat to a higher settingElevated temperature maintained until pyrogen is eliminatedLow grade fever effective defense against diseaseIntensifies effects of antiviral agents (interferon)In
24、hibits microbial growthSpeeds up physiological reactions (tissue repair),21,Complement: C proteins Complements the Immune Reactions,Consists of 26 blood proteins that work in concert to destroy bacteria and viruses Nonspecific defense that any foreign cell can activate system Complement proteins are
25、 activated by cleavage Cascade reaction 1) Classical pathway C proteins bind to receptors on foreign cell membrane 2) Alternative pathway- interaction with normal cell surface components 3) Lectin Pathway- Direct interaction with polysaccharide that contains sugar called mannan,22,Classical Pathway,
26、Two complement components contribute to inflammation - C3a and C5a Both bind to mast cells, basophils, and platelets - trigger release of histamines C5a also a potent chemoattractant for phagocytic cells,Collectively theyre called C1,Initiation,Amplification & Cascade,Series of cleavage rxns,C5 bind
27、s to membrane,23,C5b attracts other C proteins Form a ring that punctures the cell,Polymerization,Membrane attack,24,Interferons (INFs),Originally described as interfering with viral infectionsProduced in response to a viruses & a variety of antigensRNA & products of immune cellsTumor suppressive ef
28、fectsThree types of human interferona lymphocytes & macrophagesb fibroblasts & epithelial cellsg T cells,25,a and b produced in infected cells, diffuse to uninfected cells- Mediates transcription of antiviral protein in uninfected cellsAllows resistance to infection- activates “natural killer” cells
29、 (NK cells) (related to T cells but lack specificity for Ag)- maturation of B and T lymphocytes and has role in inflammation,g interferon produced by T cells- Inhibits cancer cells, activates macrophages, stimulates B cells,26,27,Defenses can be classified as either (1) innate & nonspecific or (2) acquired & specific,
