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BODY DEFENSE SYSTEM

BODY DEFENSE SYSTEM. animal/human must defend , against intruders;-pathogen…??..bacteria, virus, fungi, pathogen from air, water, food, environment…. Body defense system/immunity? DEFINITION: ability of an organism to recognize and defend itself against pathogen

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BODY DEFENSE SYSTEM

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  1. BODY DEFENSE SYSTEM

  2. animal/human must defend , against intruders;-pathogen…??..bacteria, virus, fungi, pathogen from air, water, food, environment…. Body defense system/immunity? DEFINITION: ability of an organism to recognize and defend itself against pathogen resisting the attack of many dangerous organisms.

  3. IMMUNOLOGY Chapter 1: Body defense system Chapter 2 Innate Host Defenses

  4. Host defenses that produce resistance against infection can be adaptive or innate • Innate defenses: those that act against any type of invading agent • Adaptive defenses: respond to particular agents called antigens (e.g. viruses and pathogenic bacteria) Only when our resistance fails do we become susceptible to infection by pathogens DEFINITION: Innate and Adaptive immunity

  5. Respond to antigens by producing protein antibodies • Also involve the activation of the lymphocytes • Lymphocytes: specific cells of the body’s immune system • Antibody and cellular responses are more effective against succeeding invasions by same pathogen than against initial invasions Adaptive Defenses

  6. Physical barriers • Chemical barriers • Mechanical Barrier • Cellular Barrier • Inflammation • Fever • Molecular defenses Innate Defenses

  7. Comparison between innate immunity and adaptive immunity

  8. Skin and mucous membranes protect your body and internal organs from injury and infectious agents • These two physical barriers are made of cells that line body surfaces and secrete chemicals • human beta-defensin-2 on human skin destroys pathogens by poking holes in bacterial membranes • Mucosa covers those tissues and organs of body cavity exposed to exterior 1. Physical Barriers

  9. High salt content of sweat inhibits bacteria from growing • Sweat and sebum produced by sebaceous glands have low pH that inhibits growth of bacteria • Acidic pH of stomach is a defense against intestinal pathogens • Lysozyme: present in tears, saliva, and mucus, cleaves peptidoglycan linkage in bacterial cell wall 2. Chemical Barriers

  10. Hair and mucus- nasal, respirotary system • Coughing and sneezing • Urinary flow- remove microbes in urinary tract • Tears and saliva – flush bacteria from eyes and mouth • Vomitting and diarrhea- flush bacteria from digestive tract 3. MECHANICAL BARRIERFUNCTION:- PREVENT/FLUSH INVADING MICROBES IN DIFFERENT TYPE OF MECHANICAL WAY

  11. Blood consists of about 60% liquid called plasma and 40% formed elements (cells) • Formed elements: erthyrocytes, platelets, and leukocytes • Leukocytes are defensive cells important to adaptive and innate host defenses 4. Cellular Defenses – Defensive Cells

  12. Formed cellular elements of the blood

  13. Have granular cytoplasm and an irregularly shaped, lobed nucleus • Include: • Mast cells: prevalent in connective tissue, release histamine, and associated with allergies • Basophils: release histamine which helps initiate inflammatory response • Eosinophils: present in large numbers during allergic reactions • Neutrophils (polymorphonuclear leukocytes): phagocytic cells that guard skin/mucous membranes against infection • Dendritic cells: phagocytic cells that resemble nerve cells Granulocytes

  14. Lack granular cytoplasm with round nuclei • Include: • Monocytes: phagocytic cells derived from myeloid stem cells • Lymphocytes: derived from lymphoid stem cells and contribute to adaptive host immunity • Lymphocytes circulate in blood and are found in lymph nodes, spleen, thymus and tonsils Agranulocytes

  15. Cells that literally eat or engulf materials • Monocytes, dendritic cell, neutrophils, eosinophils, • Patrol, or circulate through body, destroying dead cells and cellular debris • Guard the skin/mucous membranes against invasion by microorganisms • Macrophages(formed from monocytes): “big eaters” that destroy not only microorganisms but also larger particles Phagocytes

  16. Phagocytes digest and destroy invading microbes and foreign particles by a process called phagocytosis • Phagocytic cells must: Find Adhere to Ingest Digest the microorganisms The Process of Phagocytosis

  17. Phagocytosis of two bacterial cells by a neutrophil

  18. Phagocytes in tissues first must recognize invading microorganisms • pattern recognition receptors (PRRs) on the phagocytic cells recognize molecular patterns unique to pathogen • Phagocytes release cytokines that have specific roles in host defenses • Chemokines: -A class of cytokines that attract additional phagocytes to site of infection Chemotaxis

  19. The ability of the phagocyte cell membrane to bind to specific molecules on the surface of the microbe is called adherence • Antiphagocytic capsule: the most common means by which bacteria avoid phagocytosis • Complement system: coat microbes with antibodies to aid phagocyte in adherence • Phagosome: pseudopodia fuse and enclose microorganism within this cytoplasmic vacuole Adherence and Ingestion

  20. Phagocytic cells have several mechanisms for digesting and destroying ingested microbes • Phagolysosome: lysosomes with digestive enzymes fuse with phagosome membrane • Macrophages use other metabolic products to kill ingested microbes: • Oxygen to form hydrogen peroxide • Nitric oxide and superoxide ions Digestion

  21. What if the intruder is larger than the Macrophage/neutrophils? The killing need to be done extracellularlly by… Eosinophils- excreting toxic enzymes (MBP) –kill worm Natural killer cell- secrete cytotoxic proteins that kill intracellular Extracellular killing

  22. Refers to a set of more than 20 large regulatory proteins that play a key role in host defense • General functions of the complement system are: • Enhance phagocytosis • Lyse pathogens directly • Generate peptide fragments that regulate inflammation and immune responses • Works as a cascade: a set of reactions that amplify some effect Complement

  23. The body’s defensive response to tissue damage from microbial infection • Characterized by signs: • an increase in temperature • redness • swelling • pain at infected or injured site 5. Inflammation

  24. Steps in the process of inflammation and subsequent healing

  25. The elevation of body temperature to kill invading agents and/or inactivate their toxic products HOW? • Raises temperature above opt. temp. of pathogens • Microbial enzymes or toxins is inactivated • Increase immune response • Phagocytosis is enhanced • Antiviral interferon production is increased • Fever makes patient lie to rest.. • Increased breakdown of lysosomes causing death of infected cell and microbes. 6. Fever

  26. Involve the action of interferon and complement • Interferon: interfered with viral replication in other cells • Humans have three groups of interferon (alpha, beta, and gamma) • Antiviral enzymes 7. Molecular Defenses

  27. The mechanism by which interferons alpha and beta act

  28. A Summary of the body’s nonspecific defenses

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