2.+Immune+Defenses+and+Protection+from+Parasites

2.+Immune+Defenses+and+Protection+from+Parasites -...

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Immune Defenses   Protection from Parasites Skin ulcer due to cutaneous  infection with Leishmania Leishmania (green) in  laboratory culture
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Innate Immunity Acquired Immunity Immune Defenses Physical & chemical barriers (lysozyme, skin, mucus) Innate cellular defenses: macrophages, neutrophils, eosinophils, basophils & mast cells Humoral Immunity: B cells (plasma cells & memory cells) Cell Mediated Immunity: T cells (helper & cytotoxic cells)
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Overview of Host Resistance Resistance :  ability to ward off infections Immunity : ability of host to resist a particular infection Immune system recognize foreign  Nonspecific resistance  (innate immunity) – Acts against all microbes – No immunologic memory Specific resistance  (acquired immunity) – Responses to  specific  organisms – Immunologic memory (faster response in reinfection)
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Physical & chemical barriers (lysozyme, skin, mucus)
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Physical  barriers Chemical  barriers
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Chemical Barriers Lysozyme : in tears & saliva;  hydrolyzes bonds between sugars in  peptidoglycan portion of bacterial wall, causing bacterial lysis. Gastric juices : in stomach;  Peroxidase : in saliva;  produces superoxide “free” radicals that  damage microbes by reacting with them. Lactoferrin  found in milk and many mucosal secretions such as  tears and saliva;  sequesters iron so microbes can’t use it . Mucus : is mainly composed of  mucins , a family of large, heavily  glycosylated proteins which form gels. Mucins are bind to  pathogens as part of the immune system. Free radicals : are atoms, molecules or ions with unpaired electrons on an open shell  configuration. The unpaired electrons cause them to be highly chemically reactive. When  these react with pathogen proteins or DNA, the organism is damaged or killed.
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Physical Barriers - Respiratory system mucociliary escalator   • can be expelled by coughing or sneezing • salivation washes microbes to stomach alveolar macrophages – phagocytic cells in alveoli of lungs Skin -  composed of closely packed cells  (keratinocytes ) •  Dry, salty, low pH (5-6) •  Continuous shedding •  Normal microbiota Physical Barriers - Skin
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Barriers - Gastrointestinal tract Stomach has gastric acid Intestines – Shed columnar epithelial cells – Have secretory IgA antibodies – Have a normal microbiota Barriers - Genitourinary tract unfavorable environment – hypertonic nature of kidney medulla flushing with urine & mucus
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macrophages, dendritic cells & granulocytes (neutrophils, eosinophils, basophils & mast cells)
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