CLS-415
Nada Mohamed Ahmed ,
MD, MT (ASCP)i
Objectives
• Definition of acquired immunity
• Properities of acquired immunity
• Comppnents of acquired immunity
Initiation mechanisim
Types of acquired immunity 1. Active Immunity
2. Passive Immunity
Role of innate immunity in stimulating adaptive immune
response
Immune system
Innate (non-specific) immunity
Adaptive (specific) immunity
• Anatomic barriers (Skin, mucous
membranes)
• Antigen specificity
• Physological barriers
(temperature, pH)
• Immunological memory
• Phagocytic Barriers (cells that eat
invaders)
• Inflammatory barriers (redness,
swelling, heat and pain)
• Diversity
• Self/nonself recognition
Comparison of Innate Immunity to Adaptive
Immunity
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Definition of acquired immunity
Acquired (adaptive)
Second line of response (if innate fails)
relies on mechanisms that adapt after
infection
handled by T- and B- lymphocytes
Properties of Acquired Immunity
Acquired Immunity is more specialized than
other mechanisms of immunity.
Acquired Immunity may be a cell-mediated
or it may be a humoral immunity.
These two means of acquired immunity
interact to destroy an invading foreign body.
Properties Acquired Immunity
1 - highly specific
2 - tells the difference between “self” and
“not self” cells
(only “not self” is attacked)
3 - able to respond to millions of different
invading substances (antigens)
Components of Acquired Immunity
• The humoral immune response:
- antibodies
- antibodies are produced by B-lymphocytes when
stimulated by Ag , each B cell is capable of producing
hundreds of specific Abs per seconds .
- antibodies have the ability to recognize
and bind to the specific antigens that caused their formation
Cell mediated immune response
- caused by certain types of T-lymphocytes
- T-lymphocytes recognize foreign invaders by
surface receptors
- T-lymphocytes attack and destroy invaders directly
or by releasing soluble substances (cytokines)
Humoral and cellular immunity
(antibody mediated or cellular)
Initiation of Acquired Immunity
• Acquired immune response is initiated by:
- recognition of an antigen by certain
lymphocytes
- activation of these lymphocytes
- differentiation and proliferation into
effector cells
- effector cells eliminate antigen
- development of memory cells
- memory cells elicit a rapid and long-term
response to re-exposure
Types of ACQUIRED IMMUNITY
• The resistance that an individual acquires during life
• Two types :
1. Active Immunity
2. Passive Immunity
• Active Immunity : Resistance developed as a result
of antigenic stimulus.
• Passive Immunity : Resistance transmitted passively
in ready made form of Abs.
Active and Passive
Immunity/Vaccines
 B cells
encounter
antigens and
produce
antibodies
 Active
immunity can be
naturally or
artificially
acquired
Slide
Active Immunity
- Adaptive immunity : Adaptive response of
host to specific pathogen or antigen
- Active functioning of the host’s immune
apparatus, synthesis antibodies and
immunologically active cells
- Latent period
- Long lasting
- Secondary response is faster
- Immunological memory
- More effective and gives better protection
Passive Immunity
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Ready made form of immunity
Recipients immune system plays no active role
No antigenic stimulus
No latent period, protection effective
immediately
Transient , lasting for few weeks to days
No secondary response, diminishes with
repetition
Less effective and Inferior of active immunity
Acts immediately and ‘Instant form of Immunity’
• Active Immunity
Natural Active Immunity
Artificial Active
immunity
Natural Active Immunity :
- Results from a clinical or infection by microbe
- Measles and Poliomyelitis
- Life long following many viral infection
- Immunity following bacterial infection is less
permanent than viral infections.
• Artificial Active Immunity
- Resistance
induced by Vaccines – live or
killed microorganisms or their products
- Live vaccines : Parallels natural infection
- Gives protection for a long period
- requires booster doses (is a re-exposure to the
immunizing antigen cell. )
- Killed vaccines : Less immunogenic
- Protection lasts for a short period
- Repeated doses required
Passive Immunity
 Antibodies are obtained from
someone else
 Conferred naturally from a mother to
her foetus
 Conferred artificially from immune
serum or gamma globulin
 Immunological memory does not occur
 Protection provided by “borrowed
antibodies” is temporary.
• Passive Immunity
Natural Passive Immunity
Artificial Passive Immunity
Natural passive immunity :
- Mother to baby : Maternal antibodies, Colostrum
- Immunological independence at 3-6
months
- Active immunization of mothers during
pregnancy
improves the passive immunity in
infants
Artificial Passive Immunity :
• Treatment of infections in non immune persons.
• Confers immediate and Temporary protection
Role of innate immunity
in stimulation of
adaptive immune
response
T or B-cells need two signals
for activation
First signal
antigen recognition
Second signal
derrived by innate immunity
Principle mechanisms of
innate and adaptive immunity