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INNATE IMMUNITY CHAPTER 15. First Line of Defense  Structures, chemicals, processes that work to prevent pathogens entering the body…Barriers to Entry.

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Presentation on theme: "INNATE IMMUNITY CHAPTER 15. First Line of Defense  Structures, chemicals, processes that work to prevent pathogens entering the body…Barriers to Entry."— Presentation transcript:


2 First Line of Defense  Structures, chemicals, processes that work to prevent pathogens entering the body…Barriers to Entry  Nonspecific defenses  Includes the skin and mucous membranes of the respiratory, digestive, urinary, and reproductive systems PLAY Animation: Host Defenses

3 Skin – Physical Components of Defense  Epidermis  Outer layer composed of multiple layers of tightly packed cells  Few pathogens can penetrate these layers  Shedding of dead skin cells removes attached microorganisms  Epidermal dendritic cells (Langerhans cells)  These are able to phagocytize pathogens  Dermis  Contains protein fibers …collagen  Give skin strength and pliability to resist abrasions that could introduce microorganisms

4 Skin – Chemical Components of Defense  Perspiration secreted by sweat glands  Salt – inhibits growth of pathogen by drawing water from their cells  Antimicrobial peptides – sweat glands secret dermicidins  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

5 Mucous Membranes  Line all body cavities open to the outside environment  Epithelium  Thin, outer covering of the mucous membranes  Unlike surface epidermal cells, epithelial cells are living  Tightly packed to prevent entry of pathogens  Continual shedding of cells carries attached microorganisms away

6 Microbial Antagonism  Normal microbiota help protect the body by competing with potential pathogens  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

7 Other First-Line Defenses  Many body organs secrete chemicals with antimicrobial properties  Example: lacrimal glands that bathe the eye

8 More First Line Defenses

9 Second Line of Defense  Operates when pathogens succeed in penetrating the skin or mucous membranes  Nonspecific defense  Composed of cells, antimicrobial chemicals, and processes but no physical barriers  Many of these components are contained or originate in the blood

10 Blood  Composed of cells and portions of cells within a fluid called plasma  Plasma is mostly water containing electrolytes, dissolved gases, nutrients, and proteins  When the clotting factors (a group of plasma proteins) are removed from plasma, the remaining fluid is called serum  Other plasma proteins include complement proteins and antibodies  The cells and cell fragments in plasma are called formed elements

11 Formed Elements  Three types of formed elements  Erythrocytes – carry oxygen and carbon dioxide in the blood  Platelets – involved in blood clotting  Leukocytes – involved in defending the body against invaders  Two groups  Granulocytes  Agranulocytes

12 Granulocytes  Contain large granules that stain different colors based on the dye used  Basophils – stain blue with the basic dye methylene blue  Eosinophils – stain red/orange with the acidic dye eosin  Neutrophils – stain lilac with a mixture of acidic and basic dyes  Neutrophils and eosinophils can phagocytize pathogens  White blood cells are capable of diapedesis

13 Agranulocytes  Cytoplasm appears uniform under a light microscope  Two types  lymphocytes – most involved in adaptive immunity  monocytes – leave the blood and mature into macrophages

14 Macrophages  Phagocytic cells of the second line of defense  Wandering macrophages leave the blood via diapedesis and phagocytize throughout the body  Fixed macrophages do not move throughout the body and often phagocytize within a specific organ  Include alveolar macrophages (lungs), microglia (central nervous system), Küpffer cells (liver)  All macrophages, plus monocytes attached to endothelial cells, constitute the mononuclear phagocytic system

15 Lab Analysis of Leukocytes  The differential white blood cell count (the diff) can signal signs of disease  Increased eosinophils can indicate allergies or parasitic worm infection  Bacterial diseases often show increase in leukocytes and in neutrophils  Viral infections may show increase in lymphocytes


17 Components of the Second Line of Defense  Phagocytosis  Extracellular killing by leukocytes  Nonspecific chemical defenses  Inflammation  Fever

18 Phagocytosis  Cells capable of phagocytosis are called phagocytes PLAY Animation: Phagocytosis

19 Extracellular Killing by Leukocytes  Three Cell types that kill extracellularly  Eosinophils  Mainly attack parasitic helminths (worms) by attaching to their surface  Secrete toxins that weaken or kill the helminth  Natural killer lymphocytes (NK cells)  Secrete toxins onto the surface of virally infected cells and tumors  Neutrophils  Produce chemicals that kill nearby invaders

20 Nonspecific Chemical Defenses  Some chemicals augment phagocytosis  Some attack pathogens directly  Some enhance other features of innate immunity  Nonspecific chemical defenses includes  Lysozyme  Complement  Interferon  Defensins

21 Complement System  Set of serum proteins designated numerically according to the order of their discovery  Complement activation results in lysis of the foreign cell  Complement can be activated in several ways  Classical pathway  Complement named for the events of this originally discovered pathway…the various complement proteins act nonspecifically to “complement” the action of antibodies  Alternate pathway  Activation occurs independent of antibodies

22 Complement – Two Pathways Figure 15.10

23 Inactivation of Complement  Body’s own cells withstand complement cascade  Membrane-bound proteins on many cells bind with and break down activated complement proteins PLAY Animation: The Complement System

24 Interferons  Protein molecules released by host cells to nonspecifically inhibit the spread of viral infections

25 Inflammation  Nonspecific response to tissue damage resulting from various causes  Characterized by redness, heat, swelling, and pain  Two types  Acute  Chronic PLAY Animation: Inflammation

26 Acute vs. Chronic Inflammation  Acute inflammation  Develops quickly and is short lived  Is usually beneficial  Important in the second line of defense  Dilation and increased permeability of the blood vessels  Migration of phagocytes  Tissue repair  Chronic inflammation  Develops slowly and lasts a long time  Can cause damage to tissues

27 Increased Vascular Permeability during Inflammation

28 Events in Inflammation Figure

29 Events in Inflammation Figure

30 Fever  A body temperature over 37  C  Results when chemicals called pyrogens trigger the hypothalamus to increase the body’s core temperature  Various types of pyrogens  Bacterial toxins  Cytoplasmic contents of bacteria released by lysis  Antibody-antigen complexes  These signal for the production of interleukin-I (IL-1)

31 Fever Production  IL-1 production causes the hypothalamus to secrete prostaglandin which resets the hypothalamic “thermostat”  Communication with the brain initiates muscle contractions, increased metabolic activity, and constriction of blood vessels which raises the body’s temperature  Chills associated with fever are due to the reduced blood flow of constricted vessels  Decrease in IL-1 production results in the body’s temperature returning to normal

32 Benefits of Fever  Enhances the effects of interferons  Inhibits growth of some microorganisms  May enhance the performance of phagocytes, cells of specific immunity, and the process of tissue repair

33 A Summary of Some Nonspecific Components of the First and Second Lines of Defense Table 15.5

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