Chapter 16 Tortora

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Chapter 16 Tortora

• Innate Immunity-Nonspecific Defenses

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Types of immunity

• Innate immunity-defense present at birth
• Rapid response
• No memory component
• First line of defense and second line of defense
  is in this category
• Adaptive or specific immunity is the defense that
  kicks in once the innate has been breached
• This involves lymphocytes (T and B cells)

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First line of Defense

• Skin and mucous membrane
• Contain both physical and chemical features
• Physical-intact skin is First barrier!
• Epidermis has keratin (protein) that helps
  waterproof skin
• Cells are closely packed and dry usually
• Mucous membrane-line openings to outside
• Mucus keeps these openings moist
• Some bacteria can penetrate the membrane like
  Treponema pallidum

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Physical barriers continued

• Lacrimal apparatus-produce and drain tears
• Tears wash eye and cleans it
• Saliva also washes out mouth and dilutes the
  number of bacteria
• Very small hairs found in nose help filter air
  and trap bacteria
• Cilia in lower respiratory tract move dust and
  microorganisms trapped in mucous upward toward
  throat and you swallow it (cigarettes are toxic
  to this ciliary escalator)

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More physical barriers

• Epiglottis-prevents microbes from entering lungs
  during swallowing
• Urine-cleans urethra
• Vaginal secretions-remove microbes from female
• Defecation-removes waste
• Vomiting-rids the body of harmful substances

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Chemical factors

• Sebaceous glands produce sebum which prevents
  hair from drying out and forms a protective film
  over skin
• Contain unsaturated fatty acids which inhibit
  growth of some pathogens and fungi
• Helps provide a pH of 3-5 which also discourages
  bacterial growth
• Sweat glands produce perspiration which helps
  flush bacteria from surface of skin
• Contains lysozyme which breaks down cell wall of
  gram positive and some gram negative

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Chemical continued

• Lysozyme is also in tears, saliva, nasal
  secretions, and tissue fluids
• Alexander Fleming was studying lysozyme when he
  accidentally discovered penicillin
• Gastric juice is a mixture of HCl, enzymes and
  mucus and provides a pH of 1-3
• Some bacteria are protected by food or are not
  bothered by this acid (Clostridium botulinum and
  Staphylococcus aureus)
• some like the acid (Helicobacter pylori)

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Second line of defense

• Blood includes plasma (liquid portion) and formed
  elements (solid portion)
• During an infection the total number of WBCs
  increase (leukocytosis) or decrease (leukopenia)
• Determine white blood cell count with
  differential white blood cell count
• See table 16.1 for normal values and photos

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Types of WBCs

• Divide into 2 categories
• 1. granulocytes-large granules in cytoplasm that
  are present during staining
• Neutrophils-or polymorphonucleocytes (PMNS)
• Enter early in infection, can leave blood and
  enter infected tissue
• Most abundant type and are highly phagocytic
• http//www.unomaha.edu/hpa/blood.htmlneutrophil

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Granulocytes continued

• Eosinophils-can leave blood too
• Major function is to produce toxic proteins
  against parasites
• Increase during parasite infestation and allergy
• http//en.wikipedia.org/wiki/ImageEosinophil.jpg
• Basophils-release histamine and other substances
  that are important in allergy and inflammation
  response
• http//www.unomaha.edu/hpa/blood.htmlbasophil

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Agranulocytes

• 2. Agranulocytes-no visible granules in cytoplasm
  after staining
• Include monocytes-phagocytic after mature into
  macrophages and leave blood
• One reason your lymph nodes swell during
  infection!
• Destroy microbes and old blood cells
• The other type is the lymphocyte-including T, B,
  and Natural Killer (NK) cells-these have their
  own chapter

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Phagocytosis

• Click here for a video clip of phagocytosis
• http//highered.mcgraw-hill.com/sites/0072495855/s
  tudent_view0/chapter2/animation__phagocytosis.html
  
• Watch the video and remember the steps!
• Order of importance-initial infection-neutrophils
  are first then macrophages take over
• Never Let Monkeys Eat Bananas! (order of WBCs in
  normal differential)

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Steps in phagocytosis

• Chemotaxis
• Ingestion
• Digestion (then releases waste after eating)
• Remember to watch the movie. This one has a
  little more kick http//www.sp.uconn.edu/terry/
  Common/phago053.html
• OR http//www.edumedia-sciences.com/a82_l2-phagoc
  ytosis.html

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Microbial evasion of phagocytosis

• Some have M protein and or capsules that
  interfere with adherence
• Streptococcus pneumoniae (must trap these to
  engulf)
• Some are ingested but arent killed in phagocyte
• Staphylococcus may kill phagocyte by producing
  leukocidins
• Some can live inside phagocyte
• Coxiella burnetti (Q fever), Listeria
  monocytogenes, Shigella, Rickettsia can escape
  the phagocyte
• Mycobacterium tuberculosis, HIV, Chlamydia,
  Plasmodium can multiply inside the phagocyte and
  kills the phagocyte

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Inflammation

• Triggered by damage to tissue
• 4 signs
• Pain (dolor)
• Redness (rubor)
• Swelling (tumor)
• Heat (calor)
• May have a 5th sign-loss of function
• Functions are to remove infectious agent or limit
  its effects on body and repair or replace
  damaged tissue

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Steps in inflammation

• 1. Blood vessels dilate (vasodilation) and
  increase blood flow (causes rubor and calor)
• Increased permeability due to dilated vessels is
  responsible for edema
• Vasodilation and increased permeability are
  caused by histamine and kinins
• Prostaglandins are released by damaged cells and
  intensify effect of histamine and kinins
• Leukotrienes are produced by mast cells and
  basophils and increase permeability and help
  phagocytes attach to pathogens
• Clots may form around the infection and prevent
  spread of pathogen or toxin and help form pus

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Steps continued

• 2. phagocytes migration and phagocytosis
• Phagocytes stick to inner surface of blood
  vessels (margination) and squeeze through
  endothelial lining to enter infected area
• This is called emigration or diapedesis
• 3. tissue repair-dead and damaged tissue is
  replaced
• If only parenchyma (functional part) cells are
  involved the reconstruction will be perfect (no
  scar)
• If stroma (supporting connective tissue) is
  involved scar tissue results

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Fever

• Abnormally high temperature in response to
  infection, toxins, etc
• Hypothalamus controls body temperature
• Pyrogens reset this thermostat
• Body responds by shivering, increased metabolism,
  and blood vessels constriction
• Body temp is climbing but skin is cold causing
  the chill
• After infection the blood vessels dilate and
  sweating occurs, helping lower temperature
• Crisis is when the person sweats and skin becomes
  warm (fever is breaking)
• Fever is good defense up to a point
• Death results if fever gets 112 degrees

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Antimicrobial substances

• Complement system-complex series of 30 proteins
  produced by liver that circulate in blood and
  tissues
• Help destroy microbes by cytolysis, inflammation,
  and phagocytosis
• These proteins stay inactive until split into
  fragments called a and b
• Use C to designate which is which C1-C9
• Acts as a cascade, one triggers another.
• C3 is one of the most important!
• Have 3 pathways classical, alternative, and
  lectin
• Some bacteria can resist complement (capsules)

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More antimicrobial substances

• Interferon-IFNs antiviral proteins that are
  produced by certain cells like lymphocytes and
  macrophages AFTER viral stimulation
• These proteins interfere with viral replication
• Have found 3 types so far alpha, beta, and
  gamma
• Produced by viral infected cells and spread to
  neighboring uninfected cells, inducing them to
  make antiviral proteins that disrupt viral
  multiplication
• Studying these as possible cure for cancer, etc.

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One more time!

• Transferrins-iron binding proteins that inhibit
  bacteria growth by reducing the amount of
  available iron
• Iron overload can suppress chemotaxis and
  phagocytosis and increase risk of infection!
• Antimicrobial peptides-newly discovered, produced
  by mucous membrane cells and phagocytes
• These bind to microbial plasma membrane and cause
  lysis