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Similar to IMMUNITY.pdfImmunology = study of structure and function of the immune system • Immunity = resistance of a host to pathogens and their toxic effects • Immune system = cells, tissues, and molecules that mediate resistance to infections
IMMUNITY.pdfImmunology = study of structure and function of the immune system • Immunity = resistance of a host to pathogens and their toxic effects • Immune system = cells, tissues, and molecules that mediate resistance to infections
- 1. VOLGOGRAD STATE MEDICALUNIVERSITY DEPARTMENT OF MICROBIOLOGY Immunity. Factors of Innate & Acquired (adaptive) Immunity. Lecturer: Associate Professor of the Microbiology Department, PhD Lyudmila Viktorovna Mikhailova
- 2. Immune system – theintegrated body system of organs, tissues, cells & cell products that differentiates self from non – self & neutralizes potentially pathogenic organisms. The Latin term “IMMUNIS” means the protection against foreign agents.
- 3. • Immunology =study of structure and function of the immune system • Immunity = resistance of a host to pathogens and their toxic effects • Immune system = cells, tissues, and molecules that mediate resistance to infections
- 4. Role of theimmune system • Defense against microbes • Defense against the growth of tumor cells –kills the growth of tumor cells • Homeostasis –destruction of abnormal or dead cells (e.g. dead red or white blood cells, antigen-antibody complex)
- 5. Immunity = resistanceof a host to pathogens and their toxic effects Two types of Immunity: 1. Innate (non-specific, non-adaptive) first line of immune response relies on mechanisms that exist before infection 2. Acquired (specific, adaptive) Second line of response (if innate fails) relies on mechanisms that adapt after infection handled by T- and B- lymphocytes; one cell determines one antigenic determinant
- 6. Innate or NaturalImmunity: Immunity an organism is born with. – Genetically determined. – Resistance exist prior to the exposure to the microbe • Normal flora of throat, colon and vagina occupy receptors which prevent colonization by pathogens Acquired Immunity: Immunity that an organism develops during lifetime. – Not genetically determined. – May be acquired naturally or artificially. • Development of immunity to measles in response to infection or vaccination.
- 7. Innate immunity: mechanisms •1. Mechanical barriers / surface secretion – skin, acidic pH in stomach, cilia • 2. Humoral mechanisms – lysozymes, basic proteins, complement, interferons • 3. Cellular defense mechanisms – natural killer cells, neutrophils, basophils, eosinophils, macrophages • 4. Microbial antagonism Neutrophil NK Cell Monocyte Macrophage Basophils & Mast cells Eosinophils
- 8. First Line ofDefense 1. Mechanical barriers / surface secretion • Structures, chemicals, processes that work to prevent pathogens entering the body • Nonspecific defenses • Include the skin and mucous membranes of the respiratory, digestive, urinary, and reproductive systems
- 9. Skin – BarrierComponent of Defense – Epidermis • Outer layer composed of multiple layers of tightly packed cells –Few pathogens can penetrate these layers –Shedding of dead skin cells removes attached microorganisms • Epidermal dendritic cells (Langerhans cells) –These are able to phagocytize pathogens – Dermis • Contains protein fibers - collagen –Give skin strength and pliability to resist abrasions that could introduce microorganisms
- 10. Skin – ChemicalComponents of Defense • Perspiration secreted by sweat glands – Salt – inhibits growth of pathogen by drawing water from their cells – Antimicrobial peptides – sweat glands secret dermicidins – Lysozyme – destroys cell wall of bacteria (G+) • Sebum secreted by sebaceous (oil) glands – Helps keep skin pliable and less likely to break or tear – Lowers the pH of the skin to a level inhibitory to many bacteria
- 11. Mucous Membranes • Lineall body cavities open to the outside environment • Epithelium – Thin, outer covering of the mucous membranes – Unlike surface epidermal cells, epithelial cells are living – Tightly packed to prevent entry of pathogens – Continual shedding of cells carries attached microorganisms away
- 12. 2. Humoral mechanisms •Many body organs secrete chemicals with antimicrobial properties • Example: lacrimal glands that bathe the eye Lysozyme Complement Interferon Defensins
- 13. Complement System • Setof serum proteins designated numerically according to the order of their discovery (over 30 proteins) • Complement activation results in lysis of the foreign cell • Complement can be activated in several ways: – Classical pathway • Complement named for the events of this originally discovered pathway…the various complement proteins act nonspecifically to “complement” the action of antibodies – Alternative pathway • Activation occurs independent of antibodies – Lectin pathway (mannose-binding lectin)
- 14. Interferons Proteins usually producedby viraly infected cells * Types of interferons: 1- Alpha interferon Secreted by macrophages Induced by Viruses or Polynucleotide 2- Beta interferon Secreted by Fibroblasts Induced by Viruses 3- Gamma interferon Secreted by T- lymphocytes, Induced by Specific antigens
- 15. Interferons Protective action ofinterferons: 1) Activate T-cells 2) Activate macrophages 3) Activate NK
- 16. Components of theSecond Line of Defense • Phagocytosis • Extracellular killing by leukocytes • Nonspecific chemical defenses • Inflammation • Fever
- 17. 3. Cellular defensemechanisms Phagocytosis
- 18. Nonspecific Cellular Components 1.Activated Macrophages: Stimulated phagocytes. • Stimulated by ingestion of antigen • Larger and more effective phagocytes. • Enhanced ability to eliminate intracellular bacteria, virus- infected and cancerous cells. 2. Neutrophils • Produce chemicals that kill nearby invaders 3. Eosinophils • Mainly attack parasitic helminths (worms) by attaching to their surface • Secrete toxins that weaken or kill the helminth 4. Natural Killer (NK) Cells: • Lymphocytes that destroy virus infected and tumor cells. • Not specific. Don’t require antigen stimulation. • Not phagocytic, but must contact cell in order to lyse it.
- 19. Inflammation • Nonspecific responseto tissue damage resulting from various causes • Characterized by redness, heat, swelling, and pain Two types: • Acute inflammation – Develops quickly and is short lived – Is usually beneficial – Important in the second line of defense • Dilation and increased permeability of the blood vessels • Migration of phagocytes • Tissue repair • Chronic inflammation • Develops slowly and lasts a long time • Can cause damage to tissues
- 20. Fever • A bodytemperature over 37C • Results when chemicals called pyrogens trigger the hypothalamus to increase the body’s core temperature • Various types of pyrogens – Bacterial toxins – Cytoplasmic contents of bacteria released by lysis – Antibody-antigen complexes – These signal for the production of interleukin-I (IL-1)
- 21. 4. Microbial Antagonism •Normal microbiota helps to protect the body by competing with potential pathogens • Various activities of the normal microbiota make it hard for pathogens to compete – Consumption of nutrients makes them unavailable to pathogens – Create an environment unfavorable to other microorganisms by changing pH, production of metabolites, toxic and antibiotic-like substances (bacteriocins).
- 22. Adaptive immunity: • Basedupon resistance acquired during life • Relies on genetic events and cellular growth • Responds more slowly, over few days • Is specific – each cell responds to a single epitope on an antigen • Has anamnestic memory – repeated exposure leads to faster, stronger response • Leads to clonal expansion
- 23. Adaptive Immunity: activeand passive Active Immunity Passive Immunity Natural clinical, subclinical infection via breast milk, placenta Artificial Vaccination: Live, killed, purified antigen vaccine immune serum, immune cells
- 24. Adaptive immunity: mechanisms •Cell-mediated immune response (CMIR) –T-lymphocytes –eliminate intracellular microbes that survive within phagocytes or other infected cells • Humoral immune response (HIR) –B-lymphocytes –mediated by antibodies –eliminate extra-cellular microbes and their toxins Plasma cell (Derived from B- lymphocyte, produces antibodies)
- 25. Antibodies Proteins thatrecognize and bind to a particular antigen with very high specificity. Made in response to exposure to the antigen. One virus or microbe may have several antigenic determinant sites, to which different antibodies may bind. Each antibody has at least two identical sites that bind antigen: Antigen binding sites. Valence of an antibody: Number of antigen binding sites. Most are bivalent. Belong to a group of serum proteins called immunoglobulins (Igs).
- 26. Antibodies (immunoglobulins) •Belong tothe gamma-globulin fraction of serum proteins •Y-shaped or T-shaped polypeptides – 2 identical heavy chains – 2 identical light chains • All immunoglobulins are not antibodies •Five kinds of antibodies – IgG, IgM, IgA, IgD, IgE
- 27. A Summary ofImmunoglobulin Classes
- 28. The name antigens(Gk. anti against, genos genus) is given to organic substances of a colloid structure (proteins and different protein complexes in combination with lipids or polysaccharides) which upon injection into the body are capable of causing the production of antibodies and reacting specifically with them.
- 29. К-Ag Н-Ag О-Ag Vi-Ag Antigenic structure ofa bacterium
- 30. Antigenic structure ofa virus
- 31.