microbiology – alcamo chapter 18 – resistance and the immune system
TRANSCRIPT
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MICROBIOLOGY – ALCAMOChapter 18 – Resistance and the
Immune System
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Defense Mechanisms
• Specific Resistance– Come about in response to a particular
parasite– Directed solely at that parasite
• Nonspecific Resistance– Exists in all humans– Present from the earliest time of life
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Nonspecific Resistance
• Depends on the well-being of the individual and proper functioning of body systems
• Factors involved:– Nutrition– Fatigue– Age– Sex– Climate
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Nonspecific Resistance
• Species Immunity – diseases affecting one species will not affect another
• This type of immunity is based on– Physiological differences– Anatomical differences– Biochemical differences
• Example – chickens are resistant to anthrax because their body temperature is higher than ours (450 C)
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Nonspecific Resistance• Behavioral Immunities – exist
among various peoples of the world – way of life
• Example – India in 1700’s, people did not keep water in their houses, so mosquitoes couldn’t breed and spread malaria
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Nonspecific Resistance
• Racial Immunities – reflect the evolution of resistant humans
• Example – people in Africa with sickle cell anemia do not get malaria because the parasite can not enter the distorted RBC’s
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Mechanical Barriers• Skin and mucous membranes that
extend into our body cavities
• Disease is rare unless these barriers are penetrated
• But, skin is penetrated every day:
– Cuts
– Bug bites
– Injections
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Mechanical Barriers
• Associated defense chemicals:
– Low pH – stomach and vaginal tract
– Lytic enzymes (lysozyme) - in human tears and saliva – digest Gram + bacteria
– Bile – from the gall bladder
– Interferons – proteins produced by cells in response to viruses
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Cellular Protection
• Theory of Phagocytosis – Metchnikoff (1884, Ukraine)
• Involves cells called phagocytes:– Chemical attraction (chemotaxis) occurs
between the MO and the phagocyte– Phagocyte invaginates and pinches in to
form a phagosome– Phagosome fuses with a lysosome that
has digestive enzymes and acidic pH to digest MO
– Waste materials are expelled
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Cellular Protection
• Phagocytosis – Ameba-Like– Surround and digest MOs
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Phagocytosis Video (1 minute)
Dnatube video - phagocytosis
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Inflammation
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Inflammation
• Nonspecific defensive response to tissue damage
• Can be due to an injury, blow to the skin, bee venom, UV radiation, MO’s
• Signs of inflammation:– Rubor – red coloration from blood– Calor – warmth from heat of blood– Tumor – swelling from fluids– Dolor – pain to the local nerves
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Inflammation
• An irritant sets into motion a process that will limit the extent of the injury and repair tissue damage– Dilation of blood vessels – flow of plasma
into the tissue and fluid accumulation– Phagocytes (neutrophils and
macrophages) enter the injured area to attack the irritant
– Pus accumulates and can form an abscess or boil
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•Pus = Dead WBC, MOs and Tissue
•Greatly stimulated by B & T Cells
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Fever• Abnormally high body temperature
• The brain’s hypothalamus region maintains a body temperature of about 98.60C
• Exposure to “Pyrogens” resets the thermostat higher
• Fever inhibits the growth of certain MO’s
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.
• Useful, Up to a point!
• Pathogens sensitive to heat, so are we
• Permanent Damage/Death 106/107
• Treat to lower fever @ 102, call doctor
Fever
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Complement System
• 11 small blood (serum) proteins made in the liver
• Help antibodies and phagocytes to clear MO’s from an organism
• Attack anything with a cell membrane
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•Actions of Complement: –Weakens cell membranes
–Attracts phagocytes
–Stimulates Inflammation
•Stimulated by antibody/antigen activity
Complement System
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Natural Killer (NK) Cells
• Unique group of defensive cells that roam the body in blood and lymph
• Type of cytotoxic lymphocyte
• Kill cancer cells and virus-infected cells before the immune system is activated
• They kill cells by releasing small cytoplasmic granules of proteins that cause the target cell to die
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Two Natural Killer Cells Attack a Cancer Cell