2. • A person said to be immune when he possesses “specific
protective antibodies or cellular immunity as a result of
previous infection or immunization”.
• Specific defences
1. Active immunity :- (a) Humoral immunity
(b) Cellular immunity
(c) Combination of the above
2. Passive immunity :- (a) Normal Human Ig
(b) Specific Human Ig
(c) Animal antitoxin and
antisera
3. ACTIVE IMMUNITY
• An individuals develops as a result of infection or by
specific immunizations
• Associated with presence of antibodies or cells
having a specific action on microorganism concerned
with a particular infectious disease or on its toxin.
• Depends upon the humoral and cellular response of
the host.
• Specific for a particular disease.
4. • Acquired in 3 ways:
(a) Following clinical infection – chickenpox, measles
and rubella
(b) Following subclinical infection- polio and diphtheria
(c) Following immunization with an antigen (vaccine)
- Live attenuated vaccine, killed vaccine and toxoid
5. IMMUNE RESPONE
A. PRIMARY RESPONSE
• When an antigen is administered for the first time
to an animal or human, there is latent period of
induction of 3-10 days before antibodies appear In
the blood.
• Antibody, elicited first is entirely of the IgM type.
• IgM antibody titer rises steadily during the next 2-3
days, reaches a peak level and then declines almost
as fast as it developed.
• If the antigenic stimulus was sufficient, IgG appears
in few days, reaches in peak in 7-10 days and then
gradually falls over a period of weeks or months.
6. - Nature and extent of primary response is determined
by number of factors:
• Dose of antigen
• Nature of antigen
• Route of administration
• Adjuvants
• Presence of maternal antibody
• Nutritional status of the host
• Genetic and co-existing diseases
7. • An important outcome of primary antigenic
challenge is education of reticuloendothelium system
of the body.
• Production of memory cells or primed cells by both B
and T lymphocytes.
• These cells are responsible for immunological
memory
8. B. SECONDARY (BOOSTER) RESPONSE
• Differs in a number of ways from the primary
response:
- Shorter latent period
- Production of antibody more rapid
- Antibody more abundant
- Antibody response maintained at higher levels for
a longer period of time
- Antibody have greater capacity to bind to the
antigen
9. 1. HUMORAL IMMUNITY
• Comes from the B-cells (bone marrow derived
lymphocytes) which proliferate and manufacture
specific antibodies after antigen presentation by
macrophages.
• Antibodies circulate in the body and act directly by
neutralizing the microbe or its toxin.
• Antibodies are specific, they react with same antigen
which provoked their production.
• It will not provide protection against more than one
antigen.
10. 2. CELLULAR IMMUNITY
• Some pathogen (M. leprae, M. tuberculosis, S. typhi)
escape the bactericidal action of leukocyte.
• Stimulation of macrophages by specific stimulated T-
lymphocytes (thymus derived lymphocytes).
• Activated macrophages perform a much more
efficient phagocytic action.
• T- cell do not secrete antibody but are recognition
for antigen.
11. • On contact with antigen, the T-cells initiate a chain of
responses:
- Activation of macrophages
- Release of cytotoxic factors
- Mononuclear inflammatory reactions
- Delayed hypersensitivity reactions
- Secretions of immunological mediators
• Responsible for immunity against many diseases like
TB, brucellosis etc.
12. 3. COMBINATION OF THE BOTH
• B and T lymphoid cells, both cooperate with one
another and with certain accessory cells such as
macrophages and human K (killer) cells, and their
joint functions constitute the complex events of
immunity.
13. PASSIVE IMMUNITY
• When antibodies produced in one body (human or
animal) are transfer to another to induce protection
against disease.
• Body does not produce its own antibodies, depends
upon ready-made antibodies.
• Passive immunity may be induced by:
- Administration of an antibody-containing
preparation (immune globulin or antiserum)
- Transfer of maternal antibodies across the placenta
- Transfer of lymphocytes, to induce passive cellular
immunity
14. • Passive immunity differs from active immunity in the
following respects:
- Immunity is rapidly established
- Immunity produced is only temporary (days to
month)
- No education of the reticuloendothelial system
15. • Active immunity is superior to passive immunity
because:
- Duration of protection is long lasting
- Severe reactions are rare
- Protective efficacy is more
- Active immunization is less expensive
