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IMMUNITY

IMMUNITY. II MBBS Dr Ekta Chourasia Department of Microbiology, GMCA. Immunity. Resistance exhibited by the host towards injury caused by micro- organisms & their products. Reaction of the body against any foreign Ag. 2 types : Innate immunity Acquired immunity.

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IMMUNITY

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  1. IMMUNITY II MBBS Dr Ekta Chourasia Department of Microbiology, GMCA

  2. Immunity • Resistance exhibited by the host towards injury caused by micro- organisms & their products. • Reaction of the body against any foreign Ag. • 2 types : Innate immunity Acquired immunity Dr Ekta, Microbiology, GMCA

  3. Innate ImmunityNon specific immunity Specific immunitySpecies Racial Individual Dr Ekta, Microbiology, GMCA

  4. Acquired immunityActive PassiveNatural Artificial Natural Artificial Dr Ekta, Microbiology, GMCA

  5. Innate /Native Immunity • Resistance of an individual because of his genetic & constitutional make up, present from birth. • Not affected by prior contact with micro- organisms or by immunisations. • Innate immunity can be - Non-specific : resistance to infection in general. Specific: resistance to a particular pathogen. Dr Ekta, Microbiology, GMCA

  6. Classification of Innate Immunity Considered at 3 different levels : • Species - total or relative resistance to a pathogen shown by all the members of a species. - due to physiological & biochemical differences between the tissues of different host species. e.g. all human beings are unsusceptible to plant pathogens. Dr Ekta, Microbiology, GMCA

  7. Classification • Racial : different races within a species may show differences in susceptibility to infections. e.g. resistance to falciparum malaria in parts of Africa. • Individual : differences in innate immunity among different individuals in a race. Dr Ekta, Microbiology, GMCA

  8. Factors affecting innate immunity in an individual • AGE : low levels of immunity at the 2 extremes of life. Fetus/ Neonates - immatured immune system Old age - deteriorated immune system, physical abnormalities. • HORMONAL INFLUENCES : Increased susceptibility in endocrine disorders like DM. Corticosteroids - depress host’s resistance (antiinflammatory & antiphagocytic effect) Pregnancy - increased steroid levels Dr Ekta, Microbiology, GMCA

  9. NUTRITION : Malnutrition Results in Reduced humoral & cell mediated immunity (immunodeficiency) Paradoxically, • Some infections may not manifest in malnourished individual e.g. malaria • Some viruses do not multiply in tissues of malnourished host. Dr Ekta, Microbiology, GMCA

  10. Mechanisms of Innate Immunity A. Epithelial Surfaces 1.Skin & mucous membrane - protect against invasion by microbes. Healthy skin - high salt conc. in sweat - sebaceous secretions - long chain fatty acids & soaps Respiratory tract - nose architecture - cough reflex - mucosal secretions - phagocytes in alveoli Dr Ekta, Microbiology, GMCA

  11. Intestinal mucosa - mucus , peristalsis 2. Saliva - inhibits many micro-organisms. 3. Gastric acidity - destroys many microbes. 4. Conjunctiva - flushing action of lachrymal secretions. Tear - lysozyme - antibacterial substance - present in tissue fluid & all secretions except CSF, urine & sweat - also present in phagocytes Dr Ekta, Microbiology, GMCA

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  13. 5. Flushing action of urine6. Acidic pH of adult vagina7. Spermine & zinc in semen is antibacterial.B. Antibacterial substances in blood & tissues1. Complement system 2. Basic polypeptides – like leukins derived from leucocytes & platelets Dr Ekta, Microbiology, GMCA

  14. 4. Lactic acid in muscle & inflammatory zone5. Lactoperoxidase in milk.6. Interferons - antiviralC. Microbial antagonism- resident flora on skin & mucosa prevent colonisation by pathogens. - altered flora following oral antibiotics may lead to enterocolitis. Dr Ekta, Microbiology, GMCA

  15. D. Cellular factors1.Phagocytic cells : 2 types - polymorphonuclear leucocytes - mononuclear phagocytes: in blood & tissues monocytes macrophages Imp. link between innate & acquired immunity Chemotaxis - phagocytes are attracted to the site of infection by chemotactic factors. Dr Ekta, Microbiology, GMCA

  16. Phagocytosis • Involve - recognition & binding - ingestion and - digestion • Requires opsonins - molecules on the surface of certain bacteria which bind to the receptor on phagocytes - Opsonization. Dr Ekta, Microbiology, GMCA

  17. release of lysosomal contents phagolysosome Invagination fusion with lysosome phagosome formation Dr Ekta, Microbiology, GMCA

  18. 2. Natural killer cells Class of lymphocytes important in non- specific defense against viral infections & tumor cells. Activated by interferons & selectively kills viral infected cells & tumor cells.

  19. 3.Eosinophils • Number increases during parasitic infections & allergic conditions. • Not efficient phagocytes but their granules contain molecules that are toxic to parasites. E.Temperature - Many micro- organisms are temperature dependent e.g. tubercle bacilli, pathogenic to mammals, do not infect cold-blooded animals. - destroys infecting pathogen e.g. fever induction used to destroy T.pallidum before Pn became available for treatment. Dr Ekta, Microbiology, GMCA

  20. F. Inflammation • Non specific defense mechanism. • Tissue injury or irritation caused by the entry of pathogens or other irritants lead to inflammation. • Events that occur are – Vasodilation - Increased vascular permeability & - Cellular infiltration • Changes are brought about by chemical mediators like histamine, PGs, LTs. • Signs : redness, heat, swelling & pain. Dr Ekta, Microbiology, GMCA

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  22. G. Acute phase proteins • Present in normal serum at very low levels but their concentration rises dramatically during an infection e.g. C-reactive protein (CRP) • Enhance host resistance, prevent tissue injury & promote repair of inflammatory lesions. Dr Ekta, Microbiology, GMCA

  23. Acquired Immunity • Resistance that an individual acquires during life. • 2 types : Active acquired immunity Passive acquired immunity Dr Ekta, Microbiology, GMCA

  24. Active Immunity • Resistance developed by an individual as a result of an antigenic stimulus. • Also called Adaptive immunity. • Involves active functioning of the host’s immune system leading to the synthesis of antibodies and / or the production of immunologically active cells. Dr Ekta, Microbiology, GMCA

  25. Passive Immunity • Resistance transmitted to a recipient in a readymade form. • Preformed antibodies are administered. • No antigenic stimulus. • Host’s immune system is not actively involved. Dr Ekta, Microbiology, GMCA

  26. Active immunity Produced actively by host’s immune system Induced by infection or by immunogen Durable effective protection Immunity effective only after lag period Immunological memory present Booster effective Negative phase may occur Not applicable in the immunodeficient Passive immunity Received passively,no active host participation Readymade antibody transferred Transient, less effective Immediate immunity No memory Not effective No negative phase Applicable in immunodeficient Comparison of Active & Passive Immunity Dr Ekta, Microbiology, GMCA

  27. Active immunity • Natural active immunity– results from either a clinical or an inapparent infection by a parasite e.g. an attack of measles give lifelong immunity. • Artificial active immunity– resistance induced by vaccines. Vaccines are preparations of live or killed micro- organisms or their products. Dr Ekta, Microbiology, GMCA

  28. Passive immunity • Natural passive immunity– resistance passively transferred from mother to baby • Artificial passive immunity– resistance passively transferred by the administration of readymade antibodies. e.g.tetanus immunoglobulin • Indicated for immediate & temporary protection in a non immune host faced with the threat of infection. e.g.Rh immunoglobulin during delivery to Rh –ve mother with Rh+ve babies. Dr Ekta, Microbiology, GMCA

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