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Basic Concepts in Immunity

Basic Concepts in Immunity. Antibodies Protein substances or Globulins derived from B and T lymphocytes Formed by the body as a defensive response Titers (concentrations) can be measured to specific antigens Antigen Foreign substance or seen by the body as foreign

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Basic Concepts in Immunity

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  1. Basic Concepts in Immunity • Antibodies • Protein substances or Globulins derived from B and T lymphocytes • Formed by the body as a defensive response • Titers (concentrations) can be measured to specific antigens • Antigen • Foreign substance or seen by the body as foreign • Stimulates antibody production

  2. Host Defense Mechanisms • Active Immunity (natural and artificial) • Body produces antibodies in reaction to antigen (e.g. natural~acquired, and artificial~vaccinations) • Typically takes 2-3 weeks to confer immunity • Passive Immunity (natural and artificial) • “borrowed” in 3 ways: • Injection of serum with antibodies produced by another host (e.g., immunoglobulin) • Placental transfer (short-term immunity) • Breastfeeding • Immunity is immediate

  3. Herd Immunity • Resistance of group or population to spread of specific disease through group • Resistance due to high proportion of population immune to disease (usually due to previous immunization or infection) • Theoretically, when 85-90% of population is immune, herd immunity should protect other 10-15% • However localized outbreak could occur if not well distributed • http://www.health.harvard.edu/video/herd-immunity/

  4. Source: JHSPH Open CourseWare. Fundamentals of Epidemiology

  5. Carrier of Communicable Disease • Harbors infectious agent • Asymptomatic • No overt signs or symptoms • Can be transmitted to others • Can be carriers during incubation period or for long periods of time (chronic carriers) • “Typhoid Mary” • http://www.youtube.com/watch?v=w0dYpUjr-Cg

  6. Vaccination • Active immunity produced by vaccine • Immunity and immunologic memory similar to natural infection but without risk of disease

  7. Classification of Vaccines • Live attenuated • viral • bacterial • Inactivated

  8. Inactivated Vaccines Whole • viruses • bacteria • protein-based • toxoid • subunit • polysaccharide-based • pure • conjugate Fractional

  9. Principles of Vaccination General Rule The more similar a vaccine is to the disease-causing form of the organism, the better the immune response to the vaccine

  10. Live Attenuated Vaccines • Attenuated (weakened) form of the "wild" virus or bacterium • Must replicate to be effective • Immune response similar to natural infection • Usually produce immunity with one dose* *except those administered orally

  11. Live Attenuated Vaccines • Severe reactions possible • Interference from circulating antibody • Fragile – must be stored and handled carefully

  12. Live Attenuated Vaccines • Viral measles, mumps, rubella, varicella/zoster, yellow fever, rotavirus, intranasal influenza, rotavirus, vaccinia • Bacterial BCG, oral typhoid

  13. Inactivated Vaccines • Cannot replicate • Generally not as effective as live vaccines • Less interference from circulating antibody than live vaccines • Generally require 3-5 doses • Immune response mostly humoral • Antibody titer may diminish with time

  14. Inactivated Vaccines • Viral polio, hepatitis A, rabies, influenza* • Bacterial pertussis*, typhoid* cholera*, plague* Whole-cell vaccines *not available in the United States

  15. Inactivated Vaccines • Subunit hepatitis B, influenza, acellular pertussis, human papillomavirus, anthrax • Toxoid diphtheria, tetanus Fractional vaccines

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