1. IMMUNITY
- By Ashwini P
Saveetha Medical College

2.  Definition – Immunity
 Active Immunity
 Passive Immunity
 Herd Immunity
 Agents causing Immunity

3.  Resistance exhibited by the host towards injury
caused by microorganisms and their products
 Types
◦ Innate immunity
◦ Acquired immunity

5.  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

6. Primary Response
 Determined by,
◦ Dose and nature of antigen
◦ Route of administration
◦ Nutritional status of host
 Immunological memory
◦ Purpose of immunization

7. 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

8. Immune response

9. Active immunity mainly depends on
 Humoral immunity
 Cellular immunity
 Combination

10. 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

11.  Fundamental role in resistance to infection
 Mediated by T cells
 Initiates a chain of responses
 Responsible for immunity against many diseases
like Tb, Brucellosis

12. Joint functions of T and B lymphoid cells with
some accessory cells constitute the complex
events of immunity
Advantages of active immunity
◦ Long lasting
◦ Protective efficacy of active>passive
◦ Less expensive

13.  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

14.  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

16. Vaccination
 Injection of a weakened form of the actual antigen
that causes the disease

17. 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

18. Examples for live vaccines:
BCG vaccine
Polio vaccine
Measles vaccine
Administration of polio vaccine

19. 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

20. Examples of inactivated vaccines:
Cholera vaccine Pertussis vaccine

21. 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 infection
Cellular fractions
 Vaccines are prepared from extracted cellular
fractions
 meningococcal vaccine, pneumococcal vaccine

23. Structure of immunoglobulins:

24.  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

25.  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

26.  Materials prepared in animals
 Antitoxins prepared from non human sources are
still the mainstay of passive immunization
◦ Eg. Antisera against tetanus and diphtheria

27. SUMMARY

28.  Park's textbook of preventive and social medicine
 Textbook of microbiology-Ananthanarayanan
 Internet-google images

29. THANK YOU!!!!
NO MORE POLIO
India no longer a polio-endemic country
says WHO!