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  1. 1. IMMUNITY - By Ashwini P Saveetha Medical College
  2. 2.  Definition – Immunity Active Immunity Passive Immunity Herd Immunity Agents causing Immunity
  3. 3.  Resistance exhibited by the host towards injury caused by microorganisms and their products Types ◦ Innate immunity ◦ Acquired immunity
  4. 4.  Immunity which an individual develops as a result of infection or by specific immunization Can be acquired in three different ways ◦ Following clinical infection  Chicken pox, rubella, measles ◦ Following subclinical infection  Polio, diphtheria ◦ Following immunization
  5. 5. Primary Response Determined by, ◦ Dose and nature of antigen ◦ Route of administration ◦ Nutritional status of host Immunological memory ◦ Purpose of immunization
  6. 6. Secondary Response Differs in a number of ways ◦ Shorter latent period ◦ Production of antibodies more rapidly ◦ Antibody more abundant ◦ Antibody response maintained at higher levels for longer periods ◦ Antibody Greater capacity + Antigen
  7. 7. Immune response
  8. 8. Active immunity mainly depends on Humoral immunity Cellular immunity Combination
  9. 9. Proliferates B Cells Specific Ab’s (IgA, IgG, IgM, Secretes IgE, IgD) Antibodies are specific Acts directly by neutralizing the microbe or its toxin Efficient phagocytosis
  10. 10.  Fundamental role in resistance to infection Mediated by T cells Initiates a chain of responses Responsible for immunity against many diseases like Tb, Brucellosis
  11. 11. Joint functions of T and B lymphoid cells with some accessory cells constitute the complex events of immunityAdvantages of active immunity ◦ Long lasting ◦ Protective efficacy of active>passive ◦ Less expensive
  12. 12.  When antibodies produced in one body are transferred into another to induce protection against disease it is called passive immunity Induced by  Transfer of maternal antibodies across the placenta  Administration of antibody containing preparation Advantages – Immunity is rapidly established Disadvantages – Temporary and no immunological memory
  13. 13.  It’s the level of resistance of a community or a group of people against a particular disease Epidemic wave declines – Herd immunity builds up Elements contributing ◦ Occurrence of clinical and subclinical infections in the herd ◦ Immunization of the herd ◦ Herd structure
  14. 14. Vaccination Injection of a weakened form of the actual antigen that causes the disease
  15. 15. Vaccines Live organisms Live vaccines  BCG, Measles, Oral polio Preparation Tissue culture or Chicken embryo Lost capacity to induce full blown disease but retained their immunogenicity More potent immunizing agents than killed vaccines
  16. 16. Examples for live vaccines: BCG vaccine Polio vaccine Measles vaccine Administration of polio vaccine
  17. 17. Inactivated or killed vaccines  Cholera, pertussis vaccine Preparation Live organisms Inactivated by head or chemicals Stimulates active immunity Safe but less efficient than live vaccines
  18. 18. Examples of inactivated vaccines: Cholera vaccine Pertussis vaccine
  19. 19. Toxoids Toxins produced by organisms are detoxicated and used in the preparation of vaccines Leads to production of antibodies The Abs produced neutralize the toxic moiety produced during infectionCellular fractions Vaccines are prepared from extracted cellular fractions  meningococcal vaccine, pneumococcal vaccine
  20. 20. Structure of immunoglobulins:
  21. 21.  Normal human immunoglobulin ◦ Antibody rich fraction obtained from a pool of 1000 donors ◦ WHO has laid down definite standards for its preparation ◦ Used to prevent measles aand HepatitisA infection
  22. 22.  Specific human immunoglobulin ◦ Prepared form plasma of patients-recovered from an infection or from immunized individuals ◦ Should contain atleast 5 times the antibody potential of the standard preparation per unit volume ◦ Used mainly for prophylaxis purposes
  23. 23.  Materials prepared in animals Antitoxins prepared from non human sources are still the mainstay of passive immunization ◦ Eg. Antisera against tetanus and diphtheria
  24. 24. SUMMARY
  25. 25.  Parks textbook of preventive and social medicine Textbook of microbiology-Ananthanarayanan Internet-google images
  26. 26. THANK YOU!!!! NO MORE POLIOIndia no longer a polio-endemic countrysays WHO!