3. Resistance exhibited by the host towards injury
caused by microorganisms and their products
Types
◦ Innate immunity
◦ Acquired immunity
4.
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
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
15.
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
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
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
