Lecture%2017%20Immune%20defenses

Lecture%2017%20Immune%20defenses - 3/19/2009 Drawing blood...

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3/19/2009 1 Immune defenses: innate and adaptive Drawing blood 1 Physiological and immune defenses Limit replication or destroy Host Resistance Begins Well Before Infection pathogen • Behavioral defenses Avoid disease Physically remove parasites 2 Physical defenses that block entry • Pathogens that enter via skin – Cuts and abrasions – Biting vectors – Burrow directly into skin • Challenges – Skin is thick (for a microbe) – Relatively impermeable 3 • Pathogens that enter via ingestion or inhalation – Penetrate epithelium in lungs, gut, urogenital tract Physical defenses that block entry 4 – Migrate to blood, lungs, or other host tissues for growth and replication • Challenges to infection – Fluids, Cilia – Commensal microbes Once inside the host… Immune defenses • A defense system that protects the body from “non-self” • Purpose is to attack or Purpose is to attack or eliminate foreign material • Assumes successful colonization or invasion (transmission has occurred) 5 Innate – Immediate, generally non-specific, animal could become re infected if re exposed Innate vs. adaptive defenses could become re-infected if re-exposed Adaptive - specificity and memory to block re-infection, but with a time delay 6
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3/19/2009 2 Innate defenses 1. Inflammation response • Results in increased blood flow at site of infection or injury • Damaged tissue chemically attracts phagocytic cells • Engulf bacteria, foreign material, dead cells 7 Innate defenses 2. Phagocytosis • Phagocytic leukocytes – engulf extracellular pathogens & destroy with powerful enzymes – Neutrophils (=heterophils) – Macrophages - arrive later – Eosinophils attack macroparasites 8 Vertebrate Immunity: Major Players 9 Innate Responses: Major Players Basophils (enhance inflammatory response) Neutrophils (phagocyte; binds to and ingests extracellular bacteria) Eosinophil (attacks large extacellular parasites such as Innate helminths by injecting destructive enzymes into parasite tissues) } 10 Innate defenses 3. Complement cascade • Blood serum molecules (~20) released at site of inflammation • Attach to exterior of target foreign cells to enhance phagocytosis (opsonization) • Membrane Attack Complex (MAC) – • Demolishes lipid membranes of gram-negative bacteria and viral envelope proteins 11 Invertebrate immunity • Innate / generalized responses 1. Phagocytosis 2. Antimicrobial compounds 3. Melanization 4. Encapsulation 12
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3/19/2009 3 1. 1. Hemocytes Hemocytes = WBCs of inverts = WBCs of inverts Hemolymph = non-cellular component of invertebrate blood Note: No “red blood cells” No red blood cells Several major cell types: Granulocytes = phagocytic cells Plasmatocytes = encapsulation and aggregation 13 2. 2. Melanization Melanization and and encapsulation Melanization: Lay down melanin to ‘wall off’ smaller parasites (coat them in a layer of dark material) Encapsulation: larger parasites are surrounded by phagocytes and then melanin production that walls them off from hemocoel.
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Lecture%2017%20Immune%20defenses - 3/19/2009 Drawing blood...

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